Number of Schroeder n-paths containing no FFs.

Terms

a(0) =1a(1) =2a(2) =5a(3) =18a(4) =70a(5) =293a(6) =1283a(7) =5808a(8) =26960a(9) =127628a(10) =613814a(11) =2990681a(12) =14730713a(13) =73229291a(14) =366936231a(15) =1851352820a(16) =9397497758a(17) =47957377934a(18) =245903408244