a(n) = (8*n + 2)^4.

Terms

a(0) =16a(1) =10000a(2) =104976a(3) =456976a(4) =1336336a(5) =3111696a(6) =6250000a(7) =11316496a(8) =18974736a(9) =29986576a(10) =45212176a(11) =65610000a(12) =92236816a(13) =126247696a(14) =168896016a(15) =221533456a(16) =285610000a(17) =362673936a(18) =454371856a(19) =562448656