a(n) = (8*n + 5)^6.

Terms

a(0) =15625a(1) =4826809a(2) =85766121a(3) =594823321a(4) =2565726409a(5) =8303765625a(6) =22164361129a(7) =51520374361a(8) =107918163081a(9) =208422380089a(10) =377149515625a(11) =646990183449