a(n) = (9*n + 7)^6.

Terms

a(0) =117649a(1) =16777216a(2) =244140625a(3) =1544804416a(4) =6321363049a(5) =19770609664a(6) =51520374361a(7) =117649000000a(8) =243087455521a(9) =464404086784a(10) =832972004929