a(n) = (2/3)*n*(n^3 - 6*n^2 + 11*n - 3).

Terms

a(0) =0a(1) =2a(2) =4a(3) =6a(4) =24a(5) =90a(6) =252a(7) =574a(8) =1136a(9) =2034a(10) =3380a(11) =5302a(12) =7944a(13) =11466a(14) =16044a(15) =21870a(16) =29152a(17) =38114a(18) =48996a(19) =62054a(20) =77560a(21) =95802a(22) =117084a(23) =141726a(24) =170064a(25) =202450a(26) =239252a(27) =280854a(28) =327656a(29) =380074