a(n) = n*(n^2+3*n-1)/3.

Terms

a(0) =0a(1) =1a(2) =6a(3) =17a(4) =36a(5) =65a(6) =106a(7) =161a(8) =232a(9) =321a(10) =430a(11) =561a(12) =716a(13) =897a(14) =1106a(15) =1345a(16) =1616a(17) =1921a(18) =2262a(19) =2641a(20) =3060a(21) =3521a(22) =4026a(23) =4577a(24) =5176a(25) =5825a(26) =6526a(27) =7281a(28) =8092a(29) =8961