a(n) = (9*n + 6)^4.

Terms

a(0) =1296a(1) =50625a(2) =331776a(3) =1185921a(4) =3111696a(5) =6765201a(6) =12960000a(7) =22667121a(8) =37015056a(9) =57289761a(10) =84934656a(11) =121550625a(12) =168896016a(13) =228886641a(14) =303595776a(15) =395254161a(16) =506250000a(17) =639128961a(18) =796594176a(19) =981506241a(20) =1196883216a(21) =1445900625a(22) =1731891456a(23) =2058346161a(24) =2428912656