Binomial coefficient C(3n,n-8).

Terms

a(0) =1a(1) =27a(2) =435a(3) =5456a(4) =58905a(5) =575757a(6) =5245786a(7) =45379620a(8) =377348994a(9) =3042312350a(10) =23930713170a(11) =184509266760