a(n) = (9*n + 1)^6.

Terms

a(0) =1a(1) =1000000a(2) =47045881a(3) =481890304a(4) =2565726409a(5) =9474296896a(6) =27680640625a(7) =68719476736a(8) =151334226289a(9) =304006671424a(10) =567869252041a(11) =1000000000000