A306419 - cp's OEIS frontend

A306419 Number of set partitions of {1, ..., n} whose blocks are all singletons and pairs, not including {1, n} or {i, i + 1} for any i.

n	a(n)
0	1
1	1
2	1
3	1
4	4
5	11
6	32
7	99
8	326
9	1123
10	4064
11	15291
12	59924
13	242945
14	1019584
15	4409233
16	19648674
17	89938705
18	422744384
19	2035739041
20	10039057524
21	50610247483
22	260704414816
23	1370387233859
24	7346982653702
25	40131663286851
26	223238920709024
27	1263531826402891
28	7273434344119460

[1, 1, 1, 1, 4, 11, 32, 99, 326, 1123, 4064, 15291, 59924, 242945, 1019584, 4409233, 19648674, 89938705, 422744384, 2035739041, 10039057524, 50610247483, 260704414816, 1370387233859, 7346982653702, 40131663286851, 223238920709024, 1263531826402891, 7273434344119460]

cp's OEIS Frontend

A306419 Number of set partitions of {1, ..., n} whose blocks are all singletons and pairs, not including {1, n} or {i, i + 1} for any i.

Table of values

List of values