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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.

A001147 Double factorial of odd numbers: a(n) = (2*n-1)!! = 1*3*5*...*(2*n-1).

Table of values

n a(n)
0 1
1 1
2 3
3 15
4 105
5 945
6 10395
7 135135
8 2027025
9 34459425
10 654729075
11 13749310575
12 316234143225
13 7905853580625
14 213458046676875
15 6190283353629375
16 191898783962510625
17 6332659870762850625
18 221643095476699771875
19 8200794532637891559375
20 319830986772877770815625

List of values

[1, 1, 3, 15, 105, 945, 10395, 135135, 2027025, 34459425, 654729075, 13749310575, 316234143225, 7905853580625, 213458046676875, 6190283353629375, 191898783962510625, 6332659870762850625, 221643095476699771875, 8200794532637891559375, 319830986772877770815625]

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

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