$(3n-3)(x^2+y^2+z^2)=(9n+1)(xy+yz+zx)\implies$
$(7 + 3 n) \Biggl(6 (n - 1) x - (1 + 9 n) (y + z)\Biggr)^2 =\\ 5 (-1 + 3 n) \Bigl(\Biggl(y (7 + 3 n) + z (1 + 9 n)\Biggr)^2 - 24 (-1 + n) (2 + 3 n) z^2\Bigl)$
Let $n,z$ as parameters, then this equation have Pell form.
gp-code:
nxyz()=
{
for(n=2, 55,
n19= 1+9*n; n73= 7+3*n;
D= 5*(3*n-1)*n73;
if(!issquare(D),
C= -5*(3*n-1)*24*(n-1)*(2+3*n)*n73;
Q= bnfinit('x^2-D, 1);
fu= Q.fu[1]; \\print("Fundamental Unit: "fu);
N= bnfisintnorm(Q, C); \\print("Fundamental Solutions (Norm): "N"\n");
for(i=1, #N, ni= N[i];
for(j=0, 3,
s= lift(ni*fu^j);
X= abs(polcoeff(s, 0)); Y= abs(polcoeff(s, 1));
if(X^2-D*Y^2==C,
y= (Y-n19)/n73;
x= (X/n73+n19*(y+1))/6/(n-1);
z= lcm(denominator(x),denominator(y));
x= x*z; y= y*z;
if(3*(n - 1)*(x^2 + y^2 + z^2) == (9*n + 1)*(x*y + y*z + z*x),
print("("n", "x", "y", "z")")
)
)
)
)
)
)
};
Output $(n,x,y,z)$:
? \r nxyz.gp
? nxyz()
(2, 263, 3, 39)
(2, 263, 39, 3)
(2, 13, 1, 1)
(2, 2029, 313, 13)
(12, 31259, 9501, 645)
(12, 17390279, 5863461, 15)
(12, 17008338675311, 5734707254439, 645)
(12, 8996620057194221, 3033393402029559, 15)
(12, 23, -3, 15)
(12, 54305687, 18309183, 645)
(12, 28726047317, 9685570983, 15)
(12, 28095079670561213, 9472827435234027, 645)
(12, 27, 3, 5)
(12, 248102969, 83641041, 7095)
(12, 131244443339, 44251732701, 165)
(12, 128361659301988751, 43279743717614349, 7095)
(12, 22431, 7209, 215)
(12, 418643, 140877, 165)
(12, 409856470367, 138191431653, 7095)
(12, 216795018826247, 73096849207503, 165)
(12, 335, -9, 129)
(12, 331085, 111627, 3)
(12, 323820154601, 109182549915, 129)
(12, 171285800223257, 57752490708225, 3)
(12, 345, 99, 11)
(12, 1033625, 348291, 129)
(12, 546912497, 184402665, 3)
(12, 534899570406731, 180352267551945, 129)
(12, 79, 25, 1)
(12, 4720355, 1589181, 1419)
(12, 2498750495, 842504487, 33)
(12, 2443865517463541, 823998956160435, 1419)
(12, 48157, 16165, 43)
(12, 7895, 2607, 33)
(12, 7803215405, 2631010371, 1419)
(12, 4127539903577, 1391684013555, 33)
(12, 157553, 53097, 15)
(12, 154129532603, 51967905117, 645)
(12, 81527354638727, 27488605506693, 15)
(12, 79736606139995013647, 26884818234807767943, 645)
(12, 490499, 164301, 645)
(12, 260315351, 87770589, 15)
(12, 254597561009591, 85842745033119, 645)
(12, 134670267767599349, 45406819349798631, 15)
(12, 2230517, 740223, 7095)
(12, 1189336493, 401008707, 165)
(12, 1163213123733593, 392200959043377, 7095)
(12, 615285638339258987, 207456065037378333, 165)
(12, 3389, 891, 165)
(12, 3714100769, 1252272681, 7095)
(12, 1964596066931, 662403514509, 165)
(12, 1921443711015792671, 647853820469569989, 7095)
(12, 2534577, 854223, 215)
(12, 1340961597, 452132463, 5)
(12, 1311507385382253, 442201384990917, 215)
(12, 693726405183032343, 233903964702072237, 5)
(12, 4269, 1431, 5)
(12, 4187619141, 1411940589, 215)
(12, 2215056036591, 746851186749, 5)
(12, 2166402326572054479, 730446599032512561, 215)
(12, 19423, 6457, 55)
(12, 19132518907, 6450913843, 2365)
(12, 10120215768577, 3412236544783, 55)
(12, 9897925210224031573, 3337286762762271847, 2365)
(12, 55219, 14971, 2365)
(12, 32313529, 10895071, 55)
(12, 31603898624581, 10655897094799, 2365)
(12, 16716992394487381, 5636473932303709, 55)
(12, 48157, 16165, 43)
(12, 25530439, 8608105, 1)
(12, 24969665338195, 8419030436497, 43)
(12, 13207791558649195, 4453275509545459, 1)
(12, 79, 25, 1)
(12, 79727587, 26881705, 43)
(12, 42172242835, 14219229259, 1)
(12, 41245929443880625, 13906903863923347, 43)
(12, 345, 99, 11)
(12, 364261137, 122817255, 473)
(12, 192677832909, 64965249525, 11)
(12, 188445663972161535, 63538287723634977, 473)
(12, 335, -9, 129)
(12, 615189, 207405, 11)
(12, 601703642247, 202876618065, 473)
(12, 318273240551715, 107312295261369, 11)
(12, 22431, 7209, 215)
(12, 12151779, 4097211, 5)
(12, 11884877546769, 4007228148111, 215)
(12, 6286547425375101, 2119637303837199, 5)
(12, 27, 3, 5)
(12, 37947657, 12794463, 215)
(12, 20072833773, 6767964087, 5)
(12, 19631933953623333, 6619305755429517, 215)
(12, 23, -3, 15)
(12, 173372911, 58452229, 2365)
(12, 91709376799, 30921681241, 55)
(12, 89694980300581339, 30242486590433491, 2365)
(12, 31259, 9501, 645)
(12, 292687, 98593, 55)
(12, 286394466067, 96563714203, 2365)
(12, 151489354754713, 51077716550047, 55)
(21, 1417, 426, 48)
(21, 83142331513, 29578439082, 336)
(21, 91315532516753401, 32486110508186634, 48)
(21, 4914317238221204673953257, 1748301175858017549085194, 336)
(21, 2954, 1037, 8)
(21, 87347683, 31073934, 336)
(21, 95935286323747, 34129618776174, 48)
(21, 5162937983728230318259, 1836749666389321064622, 336)
(21, 12839986, 4567617, 168)
(21, 20199, 7158, 16)
(21, 1089383306103, 387555385974, 112)
(21, 1196473731707640183, 425653520240554902, 16)
(21, 166, 27, 24)
(21, 1144496109, 407161938, 112)
(21, 1257004661384493, 447187802705394, 16)
(21, 67648071535180409104413, 24066253210037399689266, 112)
(21, 162, 51, 4)
(21, 376240009, 133849602, 168)
(21, 413226300173881, 147008015858322, 24)
(21, 22238551035757462803577, 7911513042504815726946, 168)
(21, 164382, 58473, 4)
(21, 394819, 140166, 168)
(21, 434131875763, 154445313942, 24)
(21, 23363623933881420691, 8311765239375213222, 168)
(21, 71, 14, 8)
(21, 4929739847, 1753787774, 56)
(21, 5414351751364439, 1926191793195182, 8)
(21, 291383529309669591514199, 103661636443752927469598, 56)
(21, 12514, 4431, 12)
(21, 5178989, 1842362, 56)
(21, 5688269796029, 2023639966826, 8)
(21, 306124944398220177437, 108905993306325509018, 56)
(21, 9536, 3389, 2)
(21, 1702357, 605478, 84)
(21, 1869955422109, 665249129166, 12)
(21, 100635170298651434053, 35801633886681667206, 84)
(21, 1567, 426, 84)
(21, 1964558503, 698904786, 12)
(21, 105726414890938351, 37612878150289098, 84)
(21, 116119714172828328814711, 41310363777438054629874, 12)
(21, 712, 243, 6)
(21, 22308267, 7936266, 28)
(21, 24501335976387, 8716513896258, 4)
(21, 1318585507084135954491, 469095599806853388714, 28)
(21, 23361, 8262, 28)
(21, 25740885657, 9157491966, 4)
(21, 1385294206562535537, 492827665134459174, 28)
(21, 1521473772446088640861641, 541274455119923650488798, 4)
(21, 7591, 2628, 42)
(21, 8462029819, 3010423608, 6)
(21, 455400061126042903, 162011612958193764, 42)
(21, 500167578620665908843883, 177937956269400884789592, 6)
(21, 438, 144, 7)
(21, 8890117, 3162708, 6)
(21, 478439254001089, 170207959681728, 42)
(21, 525471609729598654933, 186940034319557009844, 6)
(21, 40222, 14304, 3)
(21, 100913, 35876, 14)
(21, 110874854861, 39444470048, 2)
(21, 5966938981113611201, 2122778390417863172, 14)
(21, 71, 8, 14)
(21, 116484131, 41440004, 2)
(21, 6268813025048183, 2230172097496232, 14)
(21, 6885060629573009104979, 2449406298176474029988, 2)
(21, 71, 8, 14)
(21, 38292856, 13622934, 3)
(21, 2060802551018062, 733144269794844, 21)
(21, 2263387096192637014984, 805215074623013954982, 3)
(21, 100913, 35876, 14)
(21, 40222, 14304, 3)
(21, 2165060831764, 770234849382, 21)
(21, 2377894353243482254, 845951796011137296, 3)
(21, 438, 144, 7)
(21, 501737268, 178496382, 1)
(21, 27001935493032294, 9606118873595136, 7)
(21, 29656326044900147464932, 10550436038739482164974, 1)
(21, 7591, 2628, 42)
(21, 527118, 187524, 1)
(21, 28367993280288, 10092103054086, 7)
(21, 31156672386592834974, 11084194269277534932, 1)
(21, 23361, 8262, 28)
(21, 693124, 246573, 6)
(21, 37302648961168, 13270666479129, 42)
(21, 40969637906871469348, 14575222285199263197, 6)
(21, 712, 243, 6)
(21, 39189831124, 13942044063, 42)
(21, 43042337210924968, 15312598904334339, 6)
(21, 2316404382684519800324788, 824076328347877344913071, 42)
(21, 1567, 426, 84)
(21, 9081956, 3230963, 2)
(21, 488762846529896, 173880646666007, 14)
(21, 536810049748675969988, 190973760075715894979, 2)
(21, 9536, 3389, 2)
(21, 513489899588, 182677460897, 14)
(21, 563967864007424864, 200635333861190573, 2)
(21, 30350991989079117832003172, 10797568087438115061341201, 14)
(21, 12514, 4431, 12)
(21, 675216370618, 240212732871, 84)
(21, 741592648046669506, 263826536981350143, 12)
(21, 39910204031994469833921946, 14198321609193718386673527, 84)
(21, 71, 14, 8)
(21, 709376086, 252365133, 84)
(21, 779110640492446, 277173813343269, 12)
(21, 41929305404327431789558, 14916630406186233794397, 84)
(21, 394819, 140166, 168)
(21, 164382, 58473, 4)
(21, 8847110986086, 3147418815249, 28)
(21, 9716814856799508798, 3456821775284131641, 4)
(21, 162, 51, 4)
(21, 9294696042, 3306650139, 28)
(21, 10208399269556226, 3631706212978083, 4)
(21, 549384218898584896608714, 195447104722505639044491, 28)
(21, 166, 27, 24)
(21, 12222111382, 4348097451, 168)
(21, 13423590828090502, 4775532081335883, 24)
(21, 722415803611620115127926, 257004246508466775463899, 168)
(21, 20199, 7158, 16)
(21, 12839986, 4567617, 168)
(21, 14102705137762, 5017131532161, 24)
(21, 758963618283224242642, 270006375648288958929, 168)
(21, 2954, 1037, 8)
(21, 160141821914, 56971522493, 56)
(21, 175884357987566762, 62572034929515101, 8)
(21, 9465547739462478924449018, 3367431820301536704807437, 56)
(21, 1417, 426, 48)
(21, 168243422, 59853623, 56)
(21, 184782542228846, 65737623396407, 8)
(21, 9944420270790822529598, 3537793921285983484199, 56)
(32, 71, 21, 3)
(32, 73589, 26823, 3)
(32, 68371913, 24926349, 3)
(32, 63517441391, 23156559201, 3)
(32, 6529, 2203, 103)
(32, 1711769, 607197, 9579)
(32, 1615089143, 588796113, 9579)
(32, 1500441017057, 547015896759, 9579)
(32, 1711769, 607197, 9579)
(32, 6529, 2203, 103)
(32, 6331141, 2307961, 103)
(32, 5881891363, 2144361469, 103)
(32, 71, 21, 3)
(32, 14011, 5053, 31)
(32, 13096813, 4774651, 31)
(32, 12167005897, 4435726357, 31)
(41, 5664, 2079, 4)
(41, 648230352, 238757847, 52)
(41, 438104084544, 161363670519, 4)
(41, 50039371681516272, 18430635481881327, 52)
(41, 1407, 432, 52)
(41, 11548, 4248, 3)
(41, 1319964424, 486172764, 39)
(41, 892092942628, 328578063408, 3)
(41, 1407, 432, 52)
(41, 1048839, 386304, 4)
(41, 119797591527, 44124169872, 52)
(41, 80964740524719, 29821150213344, 4)
(41, 48799, 16884, 624)
(41, 34171543, 12586068, 48)
(41, 3903020849959, 1437571098324, 624)
(41, 2637841596854623, 971576886296628, 48)
(42, 7969, 369, 2337)
(42, 16822903, 6172263, 16359)
(42, 416896849, 153681489, 2337)
(42, 504853232743, 186110082423, 16359)
(42, 19, 3, 3)
(42, 32581, 11973, 21)
(42, 806659, 297363, 3)
(42, 976841701, 360104853, 21)
(42, 71567, 25871, 287)
(42, 1788713, 659321, 41)
(42, 2166199727, 798551711, 287)
(42, 53534310233, 19734995801, 41)
(42, 7969, 369, 2337)
(42, 50181, 18261, 133)
(42, 1249443, 460563, 19)
(42, 1513090101, 557788341, 133)
(51, 85, 4, 25)
(51, 2246261, 827865, 3000)
(51, 383321759, 142194435, 1500)
(51, 260659465109, 96694303185, 3000)
(51, 11321, 765, 3000)
(51, 3240899, 1199535, 1500)
(51, 2206715249, 818598285, 3000)
(51, 93784952264, 34790491635, 375)
(51, 5549, 1185, 600)
(51, 1220231, 452115, 300)
(51, 830334581, 308020065, 600)
(51, 35288987516, 13090812615, 75)
(51, 9491, 3015, 300)
(51, 7027841, 2605965, 600)
(51, 298753751, 110825640, 75)
(51, 812603757929, 301443717885, 600)
(51, 3719, 1275, 60)
(51, 2644709, 980865, 120)
(51, 112413779, 41701020, 15)
(51, 305762950781, 113425910145, 120)
(51, 22049, 7965, 120)
(51, 951644, 352995, 15)
(51, 2588566241, 960255045, 120)
(51, 440052512699, 163242003975, 60)
(51, 201, 45, 20)
(51, 8357, 3057, 24)
(51, 358088, 132831, 3)
(51, 974014325, 361320585, 24)
(51, 79, -5, 40)
(51, 3023, 1116, 3)
(51, 8245865, 3058845, 24)
(51, 1401796619, 520010847, 12)
(51, 365, 9, 120)
(51, 28475, 10536, 15)
(51, 77568245, 28774521, 120)
(51, 13186546055, 4891684731, 60)
(51, 200, 51, 15)
(51, 656345, 243261, 120)
(51, 111636155, 41412471, 60)
(51, 75912045665, 28160353629, 120)
(51, 2060, 639, 75)
(51, 6175685, 2289849, 600)
(51, 1050149735, 389563299, 300)
(51, 714096227165, 264901336521, 600)
(51, 50585, 17709, 600)
(51, 8889635, 3297159, 300)
(51, 6045484265, 2242633461, 600)
(51, 256930931735, 95311170684, 75)
(51, 50585, 17709, 600)
(51, 6081, 2040, 125)
(51, 17502799, 6491035, 1000)
(51, 2975937381, 1103953665, 500)
(51, 2060, 639, 75)
(51, 145339, 52135, 1000)
(51, 25192641, 9344565, 500)
(51, 17131822291, 6355223815, 1000)
(51, 200, 51, 15)
(51, 55191, 20115, 200)
(51, 9479629, 3516385, 100)
(51, 6446286879, 2391316035, 200)
(51, 365, 9, 120)
(51, 79969, 29485, 100)
(51, 54573219, 20244135, 200)
(51, 2319366109, 860392660, 25)
(51, 79, -5, 40)
(51, 30141, 11145, 20)
(51, 20534671, 7617475, 40)
(51, 872720841, 323744760, 5)
(51, 201, 45, 20)
(51, 173731, 64375, 40)
(51, 7388376, 2740785, 5)
(51, 20096247859, 7454909695, 40)
(51, 85, 25, 4)
(51, 65391, 24243, 8)
(51, 2780068, 1031293, 1)
(51, 7561727343, 2805100491, 8)
(51, 531, 183, 8)
(51, 23533, 8728, 1)
(51, 64017003, 23747751, 8)
(51, 10882800265, 4037086645, 4)
(51, 5095, 1819, 40)
(51, 221385, 82116, 5)
(51, 602200975, 223392571, 40)
(51, 102373299645, 37976428041, 20)
(51, 1860, 681, 5)
(51, 5098075, 1891111, 40)
(51, 866684745, 321505581, 20)
(51, 589340567395, 218621942839, 40)
(51, 11321, 765, 3000)
(51, 17560, 6469, 25)
(51, 47957535, 17789979, 200)
(51, 8152807885, 3024367729, 100)
(51, 85, 4, 25)
(51, 405435, 150039, 200)
(51, 69020785, 25603789, 100)
(51, 46933922715, 17410620831, 200)
(52, 87265827, 32385357, 2771)
(52, 1459960973099, 541892263707, 9)
(52, 92048147287974147247338801077, 34165419367023176604883761861, 1467)
(52, 218430685030184926589186837228886079152203, 81074700323244984640952021928026879199483, 9)
(52, 2153, 783, 9)
(52, 137371539031945116491, 50988057645924749097, 1467)
(52, 325983306111787289169901189942697, 120994899822529822409179156770159, 9)
(52, 20552713344229656875318856309726948602653728259979, 7628530190173194062826133687718955675547649314569, 1467)
(52, 23625803, 8768889, 153)
(52, 1489595925019173492378773, 552891839381300285045883, 24939)
(52, 3534818113200842771018599462354087979, 1312014926773376734450543669432841913, 153)
(52, 222864490427906273879838104582592646222270862013280757, 82720391467152578056709729060723124708724980324242619, 24939)
(52, 57313, 21271, 1)
(52, 2223054898745657, 825129077826969, 24939)
(52, 5275319696432786287764084191, 1958035170005975601955549791, 153)
(52, 332600263532425146752562065682195480701388569, 123450909333536721211738813543440164698032057, 24939)
(52, 2702274161, 1003000323, 51)
(52, 47151518843, 17501181513, 489)
(52, 111890778596558634258749, 41530389113585179514643, 3)
(52, 7054530263488799352428867951839315641947, 2618422988302124226949130627353318273929, 489)
(52, 739289, 259743, 8313)
(52, 166984441427201, 61979449203681, 3)
(52, 10528095436957252290397549108559, 3907702722297823999778661509967, 489)
(52, 24983219826937040853661741235001714285233633, 9272996879072957562173947761838531097815809, 3)
(52, 739289, 259743, 8313)
(52, 1810705079410452803, 672077605152835281, 51)
(52, 114161988513920334440985788376914201, 42373391841868689101000875136611071, 8313)
(52, 270906933927627338861500970927626814362048423811, 100552257484502936920291680950911755368111882673, 51)
(52, 47151518843, 17501181513, 489)
(52, 2702274161, 1003000323, 51)
(52, 170373967572005330478362303, 63237536254916614432747929, 8313)
(52, 404298223750622602383461728470474057617, 150062969986439110857051148438085813187, 51)
(52, 57313, 21271, 1)
(52, 3613672152818956111411, 1341283102306646561761, 163)
(52, 8575260959303115911441461891717921, 3182871089622997329721870358572663, 1)
(52, 540656153380082209520978621311915847769444315844723, 200674807237596616898698488971868538441820405999809, 163)
(52, 23625803, 8768889, 153)
(52, 5393000508673, 2001714639859, 163)
(52, 12797615490235134653304247, 4750078225408443559709857, 1)
(52, 806868688454488373932933421852550096065569, 299484649364247716483553654683990289891763, 163)
(52, 2153, 783, 9)
(52, 58479301015729521, 21705704051181393, 2771)
(52, 138771655457564842236928895847, 51507737468423526106814617191, 17)
(52, 8749325506703922571740188861834180695165341777, 3247478454725897149498003876763795701034220657, 2771)
(52, 87265827, 32385357, 2771)
(52, 207101136154068758961, 76869522924283193427, 17)
(52, 13057387310438535438147005908681382883, 4846497473796114860142420438731641581, 2771)
(52, 30985241299866522929367680411548178161339775627889, 11500761225388102414754804352683627625158764415859, 17)