A transform of the large Schroeder numbers A006318.

Terms

a(0) =1a(1) =2a(2) =8a(3) =34a(4) =162a(5) =820a(6) =4338a(7) =23694a(8) =132612a(9) =756594a(10) =4384022a(11) =25729336a(12) =152627730a(13) =913674362a(14) =5512542128a(15) =33486653154a(16) =204639278346