Number of triangulated (n+2)-gons rooted at an exterior edge.

Terms

a(0) =1a(1) =1a(2) =5a(3) =12a(4) =45a(5) =143a(6) =511a(7) =1768a(8) =6330a(9) =22610a(10) =81818a(11) =297160a(12) =1086813a(13) =3991995a(14) =14733435a(15) =54587280a(16) =203000094a(17) =757398510a(18) =2834519142a(19) =10637507400a(20) =40023665682a(21) =150946230006a(22) =570534682710