A008910 Join 2n points on a line with n arcs above the line; form graph with the arcs as nodes, joining 2 nodes when the arcs cross. a(n) is the number of cases in which the graph is symmetric about middle and has no isolated nodes.
0, 1, 2, 9, 26, 122, 466, 2299, 10316, 54179
Offset: 1