Number of free Tangles of size n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =16a(5) =55a(6) =221a(7) =947a(8) =4239a(9) =19452a(10) =90791a(11) =428839a(12) =2043548a(13) =9807941