a(n) = n*(n+1)*(n+2)*(2*n^3 + 6*n^2 + 7*n - 3)/36.

Terms

a(0) =0a(1) =2a(2) =34a(3) =210a(4) =830a(5) =2520a(6) =6412a(7) =14364a(8) =29220a(9) =55110a(10) =97790a(11) =165022a(12) =266994a(13) =416780a(14) =630840a(15) =929560a(16) =1337832a(17) =1885674a(18) =2608890a(19) =3549770a(20) =4757830a(21) =6290592a(22) =8214404a(23) =10605300a(24) =13549900a(25) =17146350a(26) =21505302a(27) =26750934a(28) =33022010a(29) =40472980