Binomial coefficient C(3n,n-7).

Terms

a(0) =1a(1) =24a(2) =351a(3) =4060a(4) =40920a(5) =376992a(6) =3262623a(7) =26978328a(8) =215553195a(9) =1677106640a(10) =12777711870a(11) =95722852680a(12) =707285522580