a(n) = (n+1)(n+2)(n+3)(9n^2 + 26n + 20)/120.

Terms

a(0) =1a(1) =11a(2) =54a(3) =179a(4) =469a(5) =1050a(6) =2100a(7) =3858a(8) =6633a(9) =10813a(10) =16874a(11) =25389a(12) =37037a(13) =52612a(14) =73032a(15) =99348a(16) =132753a(17) =174591a(18) =226366a(19) =289751a(20) =366597a(21) =458942a(22) =569020a(23) =699270a(24) =852345a(25) =1031121a(26) =1238706a(27) =1478449a(28) =1753949a(29) =2069064