a(n) = n^3*(n^6 + 1)/2.

Terms

a(0) =0a(1) =1a(2) =260a(3) =9855a(4) =131104a(5) =976625a(6) =5038956a(7) =20176975a(8) =67109120a(9) =193710609a(10) =500000500a(11) =1178974511a(12) =2579891040a(13) =5302250785a(14) =10330524764a(15) =19221681375a(16) =34359740416a(17) =59293940705a(18) =99179648100a(19) =161343852319a(20) =256000004000