a(n) = (4*n+2)^4.

Terms

a(0) =16a(1) =1296a(2) =10000a(3) =38416a(4) =104976a(5) =234256a(6) =456976a(7) =810000a(8) =1336336a(9) =2085136a(10) =3111696a(11) =4477456a(12) =6250000a(13) =8503056a(14) =11316496a(15) =14776336a(16) =18974736a(17) =24010000a(18) =29986576a(19) =37015056a(20) =45212176a(21) =54700816a(22) =65610000a(23) =78074896a(24) =92236816