Find the positive integers $(2^x-1)(3^y-1)=2z^2$ have three solution $$(1,1,1),(1,2,2),(1,5,11)$$
I already know the solution of $(2^x-1)(3^y-1)=z^2$ has no solution.see:P.G.Walsh December 2006 On Diophantine equations of the form but there is a factor of 2 that seems complicated(I also searched a lot of these articles, and I didn't find any questions about the coefficient of 2,3,4 on the right.) and I didn't know anyone had studied this before. If so, please help me with the article or link,Thanks Before I have post this problem on MO