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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.

A356401 a(n) = n! * Sum_{k=1..n} Sum_{d|k} (-1)^(d+1)/(d * (k/d)!).

Table of values

n a(n)
1 1
2 2
3 9
4 25
5 150
6 841
7 6608
8 41945
9 437986
10 4364741
11 51640952
12 526219585
13 7319856206
14 102469338245
15 1671439939276
16 23909485105217
17 427384036676690
18 7518024186420421
19 149244833247716000
20 2756811766466473601
21 61545779138627817622
22 1354007126970517958885

List of values

[1, 2, 9, 25, 150, 841, 6608, 41945, 437986, 4364741, 51640952, 526219585, 7319856206, 102469338245, 1671439939276, 23909485105217, 427384036676690, 7518024186420421, 149244833247716000, 2756811766466473601, 61545779138627817622, 1354007126970517958885]

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

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