a(n) = n*((2*n + 1)*(2*n^2 + 2*n + 3) - 3*(-1)^n)/24.

Terms

a(0) =0a(1) =1a(2) =6a(3) =24a(4) =64a(5) =145a(6) =282a(7) =504a(8) =832a(9) =1305a(10) =1950a(11) =2816a(12) =3936a(13) =5369a(14) =7154a(15) =9360a(16) =12032a(17) =15249a(18) =19062a(19) =23560a(20) =28800a(21) =34881a(22) =41866a(23) =49864a(24) =58944a(25) =69225a(26) =80782a(27) =93744a(28) =108192a(29) =124265