a(n) = n^4*(n-1)*(n+1)/12.

Terms

a(0) =0a(1) =4a(2) =54a(3) =320a(4) =1250a(5) =3780a(6) =9604a(7) =21504a(8) =43740a(9) =82500a(10) =146410a(11) =247104a(12) =399854a(13) =624260a(14) =945000a(15) =1392640a(16) =2004504a(17) =2825604a(18) =3909630a(19) =5320000a(20) =7130970a(21) =9428804a(22) =12313004a(23) =15897600a(24) =20312500a(25) =25704900a(26) =32240754a(27) =40106304a(28) =49509670a(29) =60682500