a(n) = (5*n + 4)^7.

Terms

a(0) =16384a(1) =4782969a(2) =105413504a(3) =893871739a(4) =4586471424a(5) =17249876309a(6) =52523350144a(7) =137231006679a(8) =319277809664a(9) =678223072849