a(n) = (1/6)*(n^6+3*n^4+12*n^3+8*n^2).

Terms

a(0) =0a(1) =4a(2) =40a(3) =228a(4) =960a(5) =3200a(6) =8904a(7) =21560a(8) =46848a(9) =93420a(10) =173800a(11) =305404a(12) =511680a(13) =823368a(14) =1279880a(15) =1930800a(16) =2837504a(17) =4074900a(18) =5733288a(19) =7920340a(20) =10763200a(21) =14410704a(22) =19035720a(23) =24837608a(24) =32044800a(25) =40917500a(26) =51750504a(27) =64876140a(28) =80667328a(29) =99540760