a(n) = n*(n+1)*(n^4 + 2*n^3 - 2*n^2 - 3*n + 3)/2.

Terms

a(0) =0a(1) =1a(2) =63a(3) =666a(4) =3430a(5) =12195a(6) =34461a(7) =83188a(8) =178956a(9) =352485a(10) =647515a(11) =1124046a(12) =1861938a(13) =2964871a(14) =4564665a(15) =6825960a(16) =9951256a(17) =14186313a(18) =19825911a(19) =27219970a(20) =36780030a(21) =48986091a(22) =64393813a(23) =83642076a(24) =107460900a(25) =136679725a(26) =172236051a(27) =215184438