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

Terms

a(0) =256a(1) =28561a(2) =234256a(3) =923521a(4) =2560000a(5) =5764801a(6) =11316496a(7) =20151121a(8) =33362176a(9) =52200625a(10) =78074896a(11) =112550881a(12) =157351936a(13) =214358881a(14) =285610000a(15) =373301041a(16) =479785216a(17) =607573201a(18) =759333136a(19) =937890625a(20) =1146228736a(21) =1387488001a(22) =1664966416a(23) =1982119441a(24) =2342560000a(25) =2750058481a(26) =3208542736