A370390 - cp's OEIS frontend

A370390 Number of permutations of [n] whose longest block is of length 2. A block of a permutation is a maximal sequence of consecutive integers which appear in consecutive positions.

n	a(n)
0	0
1	0
2	1
3	2
4	10
5	53
6	334
7	2428
8	20009
9	184440
10	1881050
11	21034905
12	255967940
13	3367720736
14	47641219569
15	721160081974
16	11631770791362
17	199159952915293
18	3607908007376418
19	68946510671942892
20	1386140583681969289
21	29247292475233307612
22	646231776371742321826

[0, 0, 1, 2, 10, 53, 334, 2428, 20009, 184440, 1881050, 21034905, 255967940, 3367720736, 47641219569, 721160081974, 11631770791362, 199159952915293, 3607908007376418, 68946510671942892, 1386140583681969289, 29247292475233307612, 646231776371742321826]

cp's OEIS Frontend

A370390 Number of permutations of [n] whose longest block is of length 2. A block of a permutation is a maximal sequence of consecutive integers which appear in consecutive positions.

Table of values

List of values