a(n) = n*(n+1)*(n+2)/2.

Terms

a(0) =0a(1) =3a(2) =12a(3) =30a(4) =60a(5) =105a(6) =168a(7) =252a(8) =360a(9) =495a(10) =660a(11) =858a(12) =1092a(13) =1365a(14) =1680a(15) =2040a(16) =2448a(17) =2907a(18) =3420a(19) =3990a(20) =4620a(21) =5313a(22) =6072a(23) =6900a(24) =7800a(25) =8775a(26) =9828a(27) =10962a(28) =12180a(29) =13485