a(n) = n*(n+1)^2*(n+2)^2/12.

Terms

a(0) =0a(1) =3a(2) =24a(3) =100a(4) =300a(5) =735a(6) =1568a(7) =3024a(8) =5400a(9) =9075a(10) =14520a(11) =22308a(12) =33124a(13) =47775a(14) =67200a(15) =92480a(16) =124848a(17) =165699a(18) =216600a(19) =279300a(20) =355740a(21) =448063a(22) =558624a(23) =690000a(24) =845000a(25) =1026675a(26) =1238328a(27) =1483524a(28) =1766100a(29) =2090175