a(n) = n*(n + 1)*(2*n^2 + 2*n - 1)/6.

Terms

a(0) =1a(1) =11a(2) =46a(3) =130a(4) =295a(5) =581a(6) =1036a(7) =1716a(8) =2685a(9) =4015a(10) =5786a(11) =8086a(12) =11011a(13) =14665a(14) =19160a(15) =24616a(16) =31161a(17) =38931a(18) =48070a(19) =58730a(20) =71071a(21) =85261a(22) =101476a(23) =119900a(24) =140725a(25) =164151a(26) =190386a(27) =219646a(28) =252155a(29) =288145