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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.

A212443 a(n) = (1/n) * Sum_{d|n} moebius(n/d) * A002203(d)^2, where A002203 is the companion Pell numbers.

Table of values

n a(n)
1 4
2 16
3 64
4 280
5 1344
6 6496
7 32640
8 166320
9 862400
10 4523232
11 23970240
12 128063040
13 689008320
14 3728973120
15 20285199872
16 110841302880
17 608029121280
18 3346972244000
19 18480871268160
20 102328688556864
21 568014587806720
22 3160148362953120
23 17617881702072960

List of values

[4, 16, 64, 280, 1344, 6496, 32640, 166320, 862400, 4523232, 23970240, 128063040, 689008320, 3728973120, 20285199872, 110841302880, 608029121280, 3346972244000, 18480871268160, 102328688556864, 568014587806720, 3160148362953120, 17617881702072960]

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

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