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

Terms

a(0) =1a(1) =2a(2) =4a(3) =10a(4) =23a(5) =46a(6) =82a(7) =134a(8) =205a(9) =298a(10) =416a(11) =562a(12) =739a(13) =950a(14) =1198a(15) =1486a(16) =1817a(17) =2194a(18) =2620a(19) =3098a(20) =3631a(21) =4222a(22) =4874a(23) =5590a(24) =6373a(25) =7226a(26) =8152a(27) =9154a(28) =10235a(29) =11398