cp's OEIS Frontend

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.

A108305 Number of set partitions of {1, ..., n} that avoid 4-crossings.

Table of values

n a(n)
0 1
1 1
2 2
3 5
4 15
5 52
6 203
7 877
8 4139
9 21119
10 115495
11 671969
12 4132936
13 26723063
14 180775027
15 1274056792
16 9320514343
17 70548979894
18 550945607475
19 4427978077331
20 36544023687590
21 309088822019071

List of values

[1, 1, 2, 5, 15, 52, 203, 877, 4139, 21119, 115495, 671969, 4132936, 26723063, 180775027, 1274056792, 9320514343, 70548979894, 550945607475, 4427978077331, 36544023687590, 309088822019071]

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

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