a(n) = n^3*(n+1)^3*(n+2)^3/72.

Terms

a(0) =3a(1) =192a(2) =3000a(3) =24000a(4) =128625a(5) =526848a(6) =1778112a(7) =5184000a(8) =13476375a(9) =31944000a(10) =70180968a(11) =144685632a(12) =282589125a(13) =526848000a(14) =943296000a(15) =1630015488a(16) =2729559627a(17) =4444632000a(18) =7057911000a(19) =10956792000a(20) =16663911033a(21) =24874409472a(22) =36501000000a(23) =52728000000a(24) =75075609375