n^2 * (n^4 - n^2 + n + 1) / 2.

Terms

a(0) =0a(1) =1a(2) =30a(3) =342a(4) =1960a(5) =7575a(6) =22806a(7) =57820a(8) =129312a(9) =262845a(10) =495550a(11) =879186a(12) =1483560a(13) =2400307a(14) =3747030a(15) =5671800a(16) =8358016a(17) =12029625a(18) =16956702a(19) =23461390a(20) =31924200a(21) =42790671a(22) =56578390a(23) =73884372a(24) =95392800a(25) =121883125a(26) =154238526a(27) =193454730a(28) =240649192a(29) =297070635