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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.

A239688 Number of paths joining opposite corners of an n X 2 grid with every vertex appearing at most twice in the path.

Table of values

n a(n)
1 2
2 22
3 218
4 2100
5 20701
6 202664
7 1990006
8 19519656
9 191538146
10 1879225062
11 18438413081
12 180909222618
13 1775009067937
14 17415641736474
15 170875080099492
16 1676555203866592
17 16449663882025188
18 161397269556516646
19 1583562991844385082
20 15537262462108603226

List of values

[2, 22, 218, 2100, 20701, 202664, 1990006, 19519656, 191538146, 1879225062, 18438413081, 180909222618, 1775009067937, 17415641736474, 170875080099492, 1676555203866592, 16449663882025188, 161397269556516646, 1583562991844385082, 15537262462108603226]

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

Content is available under The OEIS End-User License Agreement.