(2^p+1)^2 where p is prime.A174623(2^p+1)^2 where p is prime.Terms a(0) =25a(1) =81a(2) =1089a(3) =16641a(4) =4198401a(5) =67125249a(6) =17180131329a(7) =274878955521External referencesoeis: A174623