a(n) = 27*(n-1)*(n-2)*(n-3)*(3*n-8)/2.

Terms

a(0) =0a(1) =0a(2) =324a(3) =2268a(4) =8100a(5) =21060a(6) =45360a(7) =86184a(8) =149688a(9) =243000a(10) =374220a(11) =552420a(12) =787644a(13) =1090908a(14) =1474200a(15) =1950480a(16) =2533680a(17) =3238704a(18) =4081428a(19) =5078700a(20) =6248340a(21) =7609140a(22) =9180864a(23) =10984248a(24) =13041000a(25) =15373800a(26) =18006300a(27) =20963124a(28) =24269868a(29) =27953100