Number of matched trees with 2n nodes.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =15a(5) =49a(6) =180a(7) =701a(8) =2891a(9) =12371a(10) =54564a(11) =246319a(12) =1133602a(13) =5300255a(14) =25119554a(15) =120441076a(16) =583373822a(17) =2851023191a(18) =14044428996a(19) =69677569603a(20) =347904448580