a(n) = (9*n + 5)^4.

Terms

a(0) =625a(1) =38416a(2) =279841a(3) =1048576a(4) =2825761a(5) =6250000a(6) =12117361a(7) =21381376a(8) =35153041a(9) =54700816a(10) =81450625a(11) =116985856a(12) =163047361a(13) =221533456a(14) =294499921a(15) =384160000a(16) =492884401a(17) =623201296a(18) =777796321a(19) =959512576