a(n) = (32*n^4 + 80*n^3 + 40*n^2 - 20*n + 3)*(2*n + 1)*n/15.

Terms

a(0) =0a(1) =27a(2) =850a(3) =7077a(4) =33300a(5) =113311a(6) =312390a(7) =742665a(8) =1581544a(9) =3093219a(10) =5653242a(11) =9776173a(12) =16146300a(13) =25651431a(14) =39419758a(15) =58859793a(16) =85703376a(17) =122051755a(18) =170424738a(19) =233812917a(20) =315732964a(21) =420285999a(22) =552219030a(23) =716989465a(24) =920832696a(25) =1170832755a(26) =1474996042a(27) =1842328125a(28) =2282913612a(29) =2807999095