a(n) = A007290(n+2) - 1 = 2*C(n+2,3) - 1.

Terms

a(0) =-1a(1) =1a(2) =7a(3) =19a(4) =39a(5) =69a(6) =111a(7) =167a(8) =239a(9) =329a(10) =439a(11) =571a(12) =727a(13) =909a(14) =1119a(15) =1359a(16) =1631a(17) =1937a(18) =2279a(19) =2659a(20) =3079a(21) =3541a(22) =4047a(23) =4599a(24) =5199a(25) =5849a(26) =6551a(27) =7307a(28) =8119a(29) =8989