a(n) = (6*n + 4)^6.

Terms

a(0) =4096a(1) =1000000a(2) =16777216a(3) =113379904a(4) =481890304a(5) =1544804416a(6) =4096000000a(7) =9474296896a(8) =19770609664a(9) =38068692544a(10) =68719476736a(11) =117649000000a(12) =192699928576a(13) =304006671424a(14) =464404086784a(15) =689869781056a(16) =1000000000000