A074922 - cp's OEIS frontend

A074922 Number of ways of arranging n chords on a circle (handshakes between 2n people across a table) with exactly 2 simple intersections.

n	a(n)
0	0
1	0
2	0
3	3
4	28
5	180
6	990
7	5005
8	24024
9	111384
10	503880
11	2238390
12	9806280
13	42493880
14	182530530
15	778439025
16	3300049200
17	13919756400
18	58462976880
19	244639718730
20	1020422356200
21	4244365452600
22	17610393500700
23	72907029092898

[0, 0, 0, 3, 28, 180, 990, 5005, 24024, 111384, 503880, 2238390, 9806280, 42493880, 182530530, 778439025, 3300049200, 13919756400, 58462976880, 244639718730, 1020422356200, 4244365452600, 17610393500700, 72907029092898]

cp's OEIS Frontend

A074922 Number of ways of arranging n chords on a circle (handshakes between 2n people across a table) with exactly 2 simple intersections.

Table of values

List of values