a(n) = (25*n^4-120*n^3+209*n^2-108*n)/6.

Terms

a(0) =0a(1) =1a(2) =10a(3) =57a(4) =272a(5) =885a(6) =2226a(7) =4725a(8) =8912a(9) =15417a(10) =24970a(11) =38401a(12) =56640a(13) =80717a(14) =111762a(15) =151005a(16) =199776a(17) =259505a(18) =331722a(19) =418057a(20) =520240a(21) =640101a(22) =779570a(23) =940677a(24) =1125552a(25) =1336425a(26) =1575626a(27) =1845585a(28) =2148832a(29) =2487997