a(n) = (1/24)*(n+1)*(n+3)*(n^2+22*n+88).

Terms

a(0) =0a(1) =11a(2) =37a(3) =85a(4) =163a(5) =280a(6) =446a(7) =672a(8) =970a(9) =1353a(10) =1835a(11) =2431a(12) =3157a(13) =4030a(14) =5068a(15) =6290a(16) =7716a(17) =9367a(18) =11265a(19) =13433a(20) =15895a(21) =18676a(22) =21802a(23) =25300a(24) =29198a(25) =33525a(26) =38311a(27) =43587a(28) =49385a(29) =55738