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

Terms

a(0) =1a(1) =117649a(2) =4826809a(3) =47045881a(4) =244140625a(5) =887503681a(6) =2565726409a(7) =6321363049a(8) =13841287201a(9) =27680640625a(10) =51520374361a(11) =90458382169a(12) =151334226289a(13) =243087455521a(14) =377149515625a(15) =567869252041a(16) =832972004929