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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.

A223093 Number of foldings of n labeled stamps in which leaf 1 is inwards and leaf n outwards (or leaf 1 outwards and leaf n inwards).

Table of values

n a(n)
1 0
2 0
3 2
4 4
5 16
6 38
7 132
8 342
9 1144
10 3134
11 10370
12 29526
13 97458
14 285458
15 942920
16 2822310
17 9341008
18 28440970
19 94358558
20 291294678
21 968853072
22 3025232480
23 10086634316
24 31797822936
25 106265437078
26 337731551446
27 1131117792978
28 3620119437762
29 12148796744234
30 39118879440938

List of values

[0, 0, 2, 4, 16, 38, 132, 342, 1144, 3134, 10370, 29526, 97458, 285458, 942920, 2822310, 9341008, 28440970, 94358558, 291294678, 968853072, 3025232480, 10086634316, 31797822936, 106265437078, 337731551446, 1131117792978, 3620119437762, 12148796744234, 39118879440938]

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

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