a(n) = n*(11*n^2 - 5)/6.

Terms

a(0) =0a(1) =1a(2) =13a(3) =47a(4) =114a(5) =225a(6) =391a(7) =623a(8) =932a(9) =1329a(10) =1825a(11) =2431a(12) =3158a(13) =4017a(14) =5019a(15) =6175a(16) =7496a(17) =8993a(18) =10677a(19) =12559a(20) =14650a(21) =16961a(22) =19503a(23) =22287a(24) =25324a(25) =28625a(26) =32201a(27) =36063a(28) =40222a(29) =44689