a(n) = (7*n + 3)^4.

Terms

a(0) =81a(1) =10000a(2) =83521a(3) =331776a(4) =923521a(5) =2085136a(6) =4100625a(7) =7311616a(8) =12117361a(9) =18974736a(10) =28398241a(11) =40960000a(12) =57289761a(13) =78074896a(14) =104060401a(15) =136048896a(16) =174900625a(17) =221533456a(18) =276922881a(19) =342102016a(20) =418161601