a(n) = (3*n+1)^6.

Terms

a(0) =1a(1) =4096a(2) =117649a(3) =1000000a(4) =4826809a(5) =16777216a(6) =47045881a(7) =113379904a(8) =244140625a(9) =481890304a(10) =887503681a(11) =1544804416a(12) =2565726409a(13) =4096000000a(14) =6321363049a(15) =9474296896a(16) =13841287201a(17) =19770609664a(18) =27680640625a(19) =38068692544a(20) =51520374361a(21) =68719476736a(22) =90458382169a(23) =117649000000