n^2 * (n^3 + 2n^2 + 7n - 2) / 8.

Terms

a(0) =0a(1) =1a(2) =14a(3) =72a(4) =244a(5) =650a(6) =1476a(7) =2989a(8) =5552a(9) =9639a(10) =15850a(11) =24926a(12) =37764a(13) =55432a(14) =79184a(15) =110475a(16) =150976a(17) =202589a(18) =267462a(19) =348004a(20) =446900a(21) =567126a(22) =711964a(23) =885017a(24) =1090224a(25) =1331875a(26) =1614626a(27) =1943514a(28) =2323972a(29) =2761844