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

Terms

a(0) =0a(1) =1a(2) =4a(3) =11a(4) =24a(5) =45a(6) =76a(7) =119a(8) =176a(9) =249a(10) =340a(11) =451a(12) =584a(13) =741a(14) =924a(15) =1135a(16) =1376a(17) =1649a(18) =1956a(19) =2299a(20) =2680a(21) =3101a(22) =3564a(23) =4071a(24) =4624a(25) =5225a(26) =5876a(27) =6579a(28) =7336a(29) =8149