Binomial coefficient C(3n,n-12).

Terms

a(0) =1a(1) =39a(2) =861a(3) =14190a(4) =194580a(5) =2349060a(6) =25827165a(7) =264385836a(8) =2558620845a(9) =23667689815a(10) =210980549208