cp's OEIS Frontend

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.

A334578 Double subfactorials: a(n) = (-1)^floor(n/2) * n!! * Sum_{i=0..floor(n/2)} (-1)^i/(n-2*i)!!.

Table of values

n a(n)
0 1
1 1
2 1
3 2
4 5
5 11
6 29
7 76
8 233
9 685
10 2329
11 7534
12 27949
13 97943
14 391285
15 1469144
16 6260561
17 24975449
18 112690097
19 474533530
20 2253801941
21 9965204131
22 49583642701
23 229199695012
24 1190007424825
25 5729992375301
26 30940193045449
27 154709794133126
28 866325405272573

List of values

[1, 1, 1, 2, 5, 11, 29, 76, 233, 685, 2329, 7534, 27949, 97943, 391285, 1469144, 6260561, 24975449, 112690097, 474533530, 2253801941, 9965204131, 49583642701, 229199695012, 1190007424825, 5729992375301, 30940193045449, 154709794133126, 866325405272573]