a(n) = (7*n + 5)^4.

Terms

a(0) =625a(1) =20736a(2) =130321a(3) =456976a(4) =1185921a(5) =2560000a(6) =4879681a(7) =8503056a(8) =13845841a(9) =21381376a(10) =31640625a(11) =45212176a(12) =62742241a(13) =84934656a(14) =112550881a(15) =146410000a(16) =187388721a(17) =236421376a(18) =294499921a(19) =362673936