a(n) = (n + 2)*(n^2 + n - 1).

Terms

a(0) =-2a(1) =3a(2) =20a(3) =55a(4) =114a(5) =203a(6) =328a(7) =495a(8) =710a(9) =979a(10) =1308a(11) =1703a(12) =2170a(13) =2715a(14) =3344a(15) =4063a(16) =4878a(17) =5795a(18) =6820a(19) =7959a(20) =9218a(21) =10603a(22) =12120a(23) =13775a(24) =15574a(25) =17523a(26) =19628a(27) =21895a(28) =24330a(29) =26939