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

Terms

a(0) =0a(1) =531441a(2) =34012224a(3) =387420489a(4) =2176782336a(5) =8303765625a(6) =24794911296a(7) =62523502209a(8) =139314069504a(9) =282429536481a(10) =531441000000a(11) =941480149401