a(n) = n*(n + 5)*(n + 10)*(n + 15)/24.

Terms

a(0) =0a(1) =44a(2) =119a(3) =234a(4) =399a(5) =625a(6) =924a(7) =1309a(8) =1794a(9) =2394a(10) =3125a(11) =4004a(12) =5049a(13) =6279a(14) =7714a(15) =9375a(16) =11284a(17) =13464a(18) =15939a(19) =18734a(20) =21875a(21) =25389a(22) =29304a(23) =33649a(24) =38454a(25) =43750a(26) =49569a(27) =55944a(28) =62909a(29) =70499