Number of one-sided Tangles of size n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =7a(4) =25a(5) =99a(6) =415a(7) =1849a(8) =8368a(9) =38712a(10) =181111a(11) =856833a(12) =4085025a(13) =19612082