27497

Appears in sequences

• Triangle read by rows: number of set partitions of n elements with k circular connectors.at n=60A185983
• Place two n-gons with radii 1 and 2 concentrically, forming an annular area between them. Connect all the vertices with line segments that lie entirely within that area. Then a(n) is the number of vertices in that figure.at n=28A337701
• Number of set partitions of [2n] with n circular connectors.at n=5A362944