a(n) = (7*n + 6)^4.

Terms

a(0) =1296a(1) =28561a(2) =160000a(3) =531441a(4) =1336336a(5) =2825761a(6) =5308416a(7) =9150625a(8) =14776336a(9) =22667121a(10) =33362176a(11) =47458321a(12) =65610000a(13) =88529281a(14) =116985856a(15) =151807041a(16) =193877776a(17) =244140625a(18) =303595776a(19) =373301041a(20) =454371856a(21) =547981281a(22) =655360000a(23) =777796321a(24) =916636176a(25) =1073283121a(26) =1249198336