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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A230621 Number of permutations of [n] with exactly two (possibly overlapping) occurrences of the consecutive step pattern {up}^2.

Table of values

n a(n)
0 0
1 0
2 0
3 0
4 1
5 8
6 86
7 803
8 8221
9 86214
10 966114
11 11405511
12 142934124
13 1892755874
14 26487024478
15 390658292572
16 6063383527327
17 98824236282650
18 1688354110698402
19 30179347977813309
20 563462569163994435
21 10970288500929001986
22 222384832378410907480

List of values

[0, 0, 0, 0, 1, 8, 86, 803, 8221, 86214, 966114, 11405511, 142934124, 1892755874, 26487024478, 390658292572, 6063383527327, 98824236282650, 1688354110698402, 30179347977813309, 563462569163994435, 10970288500929001986, 222384832378410907480]

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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