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.

A141221 Number of ways for each of 2n (labeled) people in a circle to look at either a neighbor or the diametrally opposite person, such that no eye contact occurs.

Table of values

n a(n)
1 0
2 30
3 156
4 826
5 4406
6 23562
7 126104
8 675074
9 3614142
10 19349430
11 103593804
12 554625898
13 2969386478
14 15897666066
15 85113810056
16 455687062274
17 2439682811478
18 13061709929934
19 69930511268508
20 374397872321626

List of values

[0, 30, 156, 826, 4406, 23562, 126104, 675074, 3614142, 19349430, 103593804, 554625898, 2969386478, 15897666066, 85113810056, 455687062274, 2439682811478, 13061709929934, 69930511268508, 374397872321626]

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

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