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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.

A018191 a(n) = Sum_{k=0..n} binomial(n, k) * k! / floor(k/2)!.

Table of values

n a(n)
0 1
1 2
2 5
3 16
4 53
5 206
6 817
7 3620
8 16361
9 80218
10 401501
11 2139512
12 11641885
13 66599846
14 388962953
15 2367284236
16 14700573137
17 94523836850
18 619674301621
19 4186249123808
20 28809504493061
21 203556335785342
22 1463877667140065
23 10777146970619636
24 80686484464418233

List of values

[1, 2, 5, 16, 53, 206, 817, 3620, 16361, 80218, 401501, 2139512, 11641885, 66599846, 388962953, 2367284236, 14700573137, 94523836850, 619674301621, 4186249123808, 28809504493061, 203556335785342, 1463877667140065, 10777146970619636, 80686484464418233]

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

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