a(n) = n^5*(n^3 + 1)/2.

Terms

a(0) =0a(1) =1a(2) =144a(3) =3402a(4) =33280a(5) =196875a(6) =843696a(7) =2890804a(8) =8404992a(9) =21552885a(10) =50050000a(11) =107259966a(12) =215115264a(13) =408051007a(14) =738163440a(15) =1281825000a(16) =2148007936a(17) =3488588649a(18) =5510925072a(19) =8493019570a(20) =12801600000a(21) =18913471731a(22) =27440513584