Binomial coefficient C(3n,n-9).

Terms

a(0) =1a(1) =30a(2) =528a(3) =7140a(4) =82251a(5) =850668a(6) =8145060a(7) =73629072a(8) =636763050a(9) =5317936260a(10) =43183019880a(11) =342700125300