Sum_{k=1..n} (k(k+1))^2/2.

Terms

a(0) =2a(1) =20a(2) =92a(3) =292a(4) =742a(5) =1624a(6) =3192a(7) =5784a(8) =9834a(9) =15884a(10) =24596a(11) =36764a(12) =53326a(13) =75376a(14) =104176a(15) =141168a(16) =187986a(17) =246468a(18) =318668a(19) =406868a(20) =513590a(21) =641608a(22) =793960a(23) =973960a(24) =1185210a(25) =1431612a(26) =1717380a(27) =2047052a(28) =2425502a(29) =2857952