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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.

A091530 a(n) = Sum_{k=1..n} H(k) k! (n-k)!, where H(k) is the k-th harmonic number.

Table of values

n a(n)
1 1
2 4
3 16
4 73
5 388
6 2396
7 17024
8 137544
9 1248816
10 12603288
11 140018688
12 1698063552
13 22318009344
14 315942698880
15 4791898275840
16 77510315197440
17 1331759355586560
18 24220225133061120
19 464796175236710400
20 9385769913543475200
21 198936154022512435200
22 4415822707430415052800

List of values

[1, 4, 16, 73, 388, 2396, 17024, 137544, 1248816, 12603288, 140018688, 1698063552, 22318009344, 315942698880, 4791898275840, 77510315197440, 1331759355586560, 24220225133061120, 464796175236710400, 9385769913543475200, 198936154022512435200, 4415822707430415052800]

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

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