a(n) = binomial(3*n,n)/(2*n+1) (enumerates ternary trees and also noncrossing trees).
A001764
a(n) = binomial(3*n,n)/(2*n+1) (enumerates ternary trees and also noncrossing trees).
Terms
- a(0) =1a(1) =1a(2) =3a(3) =12a(4) =55a(5) =273a(6) =1428a(7) =7752a(8) =43263a(9) =246675a(10) =1430715a(11) =8414640a(12) =50067108a(13) =300830572a(14) =1822766520a(15) =11124755664a(16) =68328754959a(17) =422030545335
External references
- oeis: A001764