Largest square <= 2^n.

Terms

a(0) =1a(1) =4a(2) =4a(3) =16a(4) =25a(5) =64a(6) =121a(7) =256a(8) =484a(9) =1024a(10) =2025a(11) =4096a(12) =8100a(13) =16384a(14) =32761a(15) =65536a(16) =131044a(17) =262144a(18) =524176a(19) =1048576a(20) =2096704a(21) =4194304a(22) =8386816a(23) =16777216a(24) =33547264a(25) =67108864a(26) =134212225a(27) =268435456a(28) =536848900a(29) =1073741824