a(n) = n*(n + 1)*(n + 2)*(9*n - 7)/12.

Terms

a(0) =0a(1) =1a(2) =22a(3) =100a(4) =290a(5) =665a(6) =1316a(7) =2352a(8) =3900a(9) =6105a(10) =9130a(11) =13156a(12) =18382a(13) =25025a(14) =33320a(15) =43520a(16) =55896a(17) =70737a(18) =88350a(19) =109060a(20) =133210a(21) =161161a(22) =193292a(23) =230000a(24) =271700a(25) =318825a(26) =371826a(27) =431172a(28) =497350a(29) =570865