a(n) = n^8*(n^3 + 1)/2.

Terms

a(0) =0a(1) =1a(2) =1152a(3) =91854a(4) =2129920a(5) =24609375a(6) =182238336a(7) =991545772a(8) =4303355904a(9) =15712053165a(10) =50050000000a(11) =142763014746a(12) =371719176192a(13) =896488062379