a(n) = n*(n^2 - 4*n + 5)/2.

Terms

a(0) =0a(1) =1a(2) =1a(3) =3a(4) =10a(5) =25a(6) =51a(7) =91a(8) =148a(9) =225a(10) =325a(11) =451a(12) =606a(13) =793a(14) =1015a(15) =1275a(16) =1576a(17) =1921a(18) =2313a(19) =2755a(20) =3250a(21) =3801a(22) =4411a(23) =5083a(24) =5820a(25) =6625a(26) =7501a(27) =8451a(28) =9478a(29) =10585