a(n) = (4n+1)^6.

Terms

a(0) =1a(1) =15625a(2) =531441a(3) =4826809a(4) =24137569a(5) =85766121a(6) =244140625a(7) =594823321a(8) =1291467969a(9) =2565726409a(10) =4750104241a(11) =8303765625a(12) =13841287201a(13) =22164361129a(14) =34296447249a(15) =51520374361a(16) =75418890625a(17) =107918163081