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

Terms

a(0) =0a(1) =117649a(2) =7529536a(3) =85766121a(4) =481890304a(5) =1838265625a(6) =5489031744a(7) =13841287201a(8) =30840979456a(9) =62523502209a(10) =117649000000a(11) =208422380089a(12) =351298031616a(13) =567869252041a(14) =885842380864