n^2*(n^4+1)/2.

Terms

a(0) =0a(1) =1a(2) =34a(3) =369a(4) =2056a(5) =7825a(6) =23346a(7) =58849a(8) =131104a(9) =265761a(10) =500050a(11) =885841a(12) =1493064a(13) =2413489a(14) =3764866a(15) =5695425a(16) =8388736a(17) =12068929a(18) =17006274a(19) =23523121a(20) =32000200a(21) =42883281a(22) =56690194a(23) =74018209a(24) =95551776a(25) =122070625a(26) =154458226a(27) =193710609