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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.

A004208 a(n) = n * (2*n - 1)!! - Sum_{k=0..n-1} a(k) * (2*n - 2*k - 1)!!.

Table of values

n a(n)
1 1
2 5
3 37
4 353
5 4081
6 55205
7 854197
8 14876033
9 288018721
10 6138913925
11 142882295557
12 3606682364513
13 98158402127761
14 2865624738913445
15 89338394736560917
16 2962542872271918593
17 104128401379446177601
18 3867079042971339087365
19 151312533647578564021477

List of values

[1, 5, 37, 353, 4081, 55205, 854197, 14876033, 288018721, 6138913925, 142882295557, 3606682364513, 98158402127761, 2865624738913445, 89338394736560917, 2962542872271918593, 104128401379446177601, 3867079042971339087365, 151312533647578564021477]

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

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