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.

A284747 Number of proper colorings of the 2n-gon with 2 instances of each of n colors under dihedral (rotational and reflectional) symmetry.

Table of values

n a(n)
1 0
2 1
3 4
4 54
5 1794
6 99990
7 7955460
8 848584800
9 116816051520
10 20167501253760
11 4268024125243200
12 1086711068022148800
13 327759648421871635200
14 115567595710587359539200
15 47104362677165542792243200
16 21978200228619432098036736000
17 11639211300056830532862403584000
18 6943663015969522875618267601920000

List of values

[0, 1, 4, 54, 1794, 99990, 7955460, 848584800, 116816051520, 20167501253760, 4268024125243200, 1086711068022148800, 327759648421871635200, 115567595710587359539200, 47104362677165542792243200, 21978200228619432098036736000, 11639211300056830532862403584000, 6943663015969522875618267601920000]

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

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