a(n) = n*(n+5)*(50+45*n+n^2)/24.

Terms

a(0) =24a(1) =84a(2) =194a(3) =369a(4) =625a(5) =979a(6) =1449a(7) =2054a(8) =2814a(9) =3750a(10) =4884a(11) =6239a(12) =7839a(13) =9709a(14) =11875a(15) =14364a(16) =17204a(17) =20424a(18) =24054a(19) =28125a(20) =32669a(21) =37719a(22) =43309a(23) =49474a(24) =56250a(25) =63674a(26) =71784a(27) =80619a(28) =90219a(29) =100625