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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.

A238446 Let B be a nonempty and proper subset of A_n = {1,2,...,p_n-1}, where p_n is the n-th prime. Let C be the complement of B, so that the union B and C is A_n. a(n) is half the number of sums of products of elements of B and elements of C which are divisible by p_n, when B runs through all such subsets of A_n.

Table of values

n a(n)
1 0
2 1
3 3
4 11
5 103
6 343
7 4095
8 14571
9 190651
10 9586983
11 35791471
12 1908874583
13 27487790719
14 104715393911
15 1529755308211
16 86607685141743
17 4969489243995031
18 19215358410149343
19 1117984489315857511
20 16865594581677305359
21 65588423373189982911

List of values

[0, 1, 3, 11, 103, 343, 4095, 14571, 190651, 9586983, 35791471, 1908874583, 27487790719, 104715393911, 1529755308211, 86607685141743, 4969489243995031, 19215358410149343, 1117984489315857511, 16865594581677305359, 65588423373189982911]

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

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