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

Terms

a(0) =0a(1) =1a(2) =40a(3) =405a(4) =2176a(5) =8125a(6) =23976a(7) =60025a(8) =133120a(9) =269001a(10) =505000a(11) =893101a(12) =1503360a(13) =2427685a(14) =3783976a(15) =5720625a(16) =8421376a(17) =12110545a(18) =17058600a(19) =23588101a(20) =32080000a(21) =42980301a(22) =56807080a(23) =74157865a(24) =95717376a(25) =122265625a(26) =154686376a(27) =193975965