a(n) = (n-2)*(n+3)*(n+2)/6.

Terms

a(0) =-2a(1) =-2a(2) =0a(3) =5a(4) =14a(5) =28a(6) =48a(7) =75a(8) =110a(9) =154a(10) =208a(11) =273a(12) =350a(13) =440a(14) =544a(15) =663a(16) =798a(17) =950a(18) =1120a(19) =1309a(20) =1518a(21) =1748a(22) =2000a(23) =2275a(24) =2574a(25) =2898a(26) =3248a(27) =3625a(28) =4030a(29) =4464