What could be a part of the following set of numbers: $1201, 2121, 3142, 4253, 5342$
$a) 1317$
$b) 2315$
$c) 2573$
$d) 3456$
Differences between the numbers are $920, 1021, 1111, 1089.$ It's not making sense. Increasing then decresing. So difference of difference too won't make any difference.
Adding something to the square of something too is not leading me anywhere.
Taking ratios is not helping either.
If I go after the digit sum, I get: $4, 6, 10, 14, 14.$ Digit sum of options is- $12, 11, 17, 18.$ Again dead-end.