A108307 - cp's OEIS frontend

A108307 Number of set partitions of {1, ..., n} that avoid enhanced 3-crossings (or enhanced 3-nestings).

n	a(n)
0	1
1	1
2	2
3	5
4	15
5	51
6	191
7	772
8	3320
9	15032
10	71084
11	348889
12	1768483
13	9220655
14	49286863
15	269346822
16	1501400222
17	8519796094
18	49133373040
19	287544553912
20	1705548000296
21	10241669069576
22	62201517142632
23	381749896129920
24	2365758616886432
25	14793705539872672

[1, 1, 2, 5, 15, 51, 191, 772, 3320, 15032, 71084, 348889, 1768483, 9220655, 49286863, 269346822, 1501400222, 8519796094, 49133373040, 287544553912, 1705548000296, 10241669069576, 62201517142632, 381749896129920, 2365758616886432, 14793705539872672]

cp's OEIS Frontend

A108307 Number of set partitions of {1, ..., n} that avoid enhanced 3-crossings (or enhanced 3-nestings).

Table of values

List of values