a(n) = 648 * n^6.

Terms

a(0) =0a(1) =648a(2) =41472a(3) =472392a(4) =2654208a(5) =10125000a(6) =30233088a(7) =76236552a(8) =169869312a(9) =344373768a(10) =648000000a(11) =1147971528a(12) =1934917632a(13) =3127772232a(14) =4879139328a(15) =7381125000a(16) =10871635968a(17) =15641144712a(18) =22039921152a(19) =30485730888a(20) =41472000000a(21) =55576446408a(22) =73470177792a(23) =95927256072