a(n) = n*(94 + 5*n + 25*n^2 - 5*n^3 + n^4)/120.

Terms

a(0) =0a(1) =1a(2) =3a(3) =7a(4) =15a(5) =31a(6) =62a(7) =119a(8) =218a(9) =381a(10) =637a(11) =1023a(12) =1585a(13) =2379a(14) =3472a(15) =4943a(16) =6884a(17) =9401a(18) =12615a(19) =16663a(20) =21699a(21) =27895a(22) =35442a(23) =44551a(24) =55454a(25) =68405a(26) =83681a(27) =101583a(28) =122437a(29) =146595