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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.

A275829 Number of weakly alternating permutations of the multiset {1,1,2,2,...,n,n}.

Table of values

n a(n)
0 1
1 1
2 2
3 12
4 140
5 2564
6 68728
7 2539632
8 123686800
9 7677924688
10 591741636128
11 55438330474944
12 6204888219697856
13 817697605612952384
14 125322509904814743424
15 22102340129003429880576
16 4444468680409243484516608
17 1010802175212828388101900544
18 258152577318424951261637001728

List of values

[1, 1, 2, 12, 140, 2564, 68728, 2539632, 123686800, 7677924688, 591741636128, 55438330474944, 6204888219697856, 817697605612952384, 125322509904814743424, 22102340129003429880576, 4444468680409243484516608, 1010802175212828388101900544, 258152577318424951261637001728]

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

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