a(n) = (1/24)*(n+1)*(n+6)*(n^3+26*n^2+225*n+636).

Terms

a(0) =0a(1) =159a(2) =518a(3) =1198a(4) =2358a(5) =4200a(6) =6974a(7) =10983a(8) =16588a(9) =24213a(10) =34350a(11) =47564a(12) =64498a(13) =85878a(14) =112518a(15) =145325a(16) =185304a(17) =233563a(18) =291318a(19) =359898a(20) =440750a(21) =535444a(22) =645678a(23) =773283a(24) =920228a(25) =1088625a(26) =1280734a(27) =1498968a(28) =1745898a(29) =2024258