A180564 - cp's OEIS frontend

A180564 Number of permutations of [n] having no isolated entries. An entry j of a permutation p is isolated if it is not preceded by j-1 and not followed by j+1. For example, the permutation 23178564 has 2 isolated entries: 1 and 4.

n	a(n)
0	1
1	0
2	1
3	1
4	2
5	3
6	7
7	14
8	35
9	81
10	216
11	557
12	1583
13	4444
14	13389
15	40313
16	128110
17	409519
18	1366479
19	4603338
20	16064047
21	56708713
22	206238116
23	759535545
24	2870002519
25	10986716984
26	43019064953
27	170663829777
28	690840124506
29	2832976091771
30	11831091960887
31	50040503185030

[1, 0, 1, 1, 2, 3, 7, 14, 35, 81, 216, 557, 1583, 4444, 13389, 40313, 128110, 409519, 1366479, 4603338, 16064047, 56708713, 206238116, 759535545, 2870002519, 10986716984, 43019064953, 170663829777, 690840124506, 2832976091771, 11831091960887, 50040503185030]

cp's OEIS Frontend

A180564 Number of permutations of [n] having no isolated entries. An entry j of a permutation p is isolated if it is not preceded by j-1 and not followed by j+1. For example, the permutation 23178564 has 2 isolated entries: 1 and 4.

Table of values

List of values