Generalized Catalan numbers C(2; n).

Terms

a(0) =1a(1) =1a(2) =3a(3) =13a(4) =67a(5) =381a(6) =2307a(7) =14589a(8) =95235a(9) =636925a(10) =4341763a(11) =30056445a(12) =210731011a(13) =1493303293a(14) =10678370307a(15) =76957679613a(16) =558403682307