Smallest square k == 1 (mod some n-th power), k > 1.

Terms

a(0) =4a(1) =9a(2) =9a(3) =49a(4) =225a(5) =961a(6) =3969a(7) =16129a(8) =65025a(9) =261121a(10) =1046529a(11) =4190209a(12) =16769025a(13) =67092481a(14) =268402689a(15) =1073676289a(16) =4294836225a(17) =17179607041a(18) =68718952449a(19) =274876858369