Number of symmetric non-crossing connected graphs on n equidistant nodes on a circle.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =10a(5) =32a(6) =64a(7) =231a(8) =462a(9) =1792a(10) =3584a(11) =14586a(12) =29172a(13) =122880a(14) =245760a(15) =1062347a(16) =2124694a(17) =9371648a(18) =18743296a(19) =84021990a(20) =168043980a(21) =763363328a(22) =1526726656a(23) =7012604550a(24) =14025209100a(25) =65028489216a(26) =130056978432a(27) =607892634420