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A065293
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Number of values of s, 0 <= s <= n-1, such that 2^s mod n = s.
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2
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1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 1, 1, 1, 0, 0, 0, 0, 1, 0, 1, 2, 0, 0, 1, 0, 2, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 0, 1, 2, 1, 1, 1, 0, 0, 3, 0, 0, 1, 1, 2, 0, 1, 2, 1, 0, 2, 0, 2, 0, 1, 1, 1, 1, 0, 2, 1, 0, 0, 0, 2, 1, 1, 1, 1, 1, 0, 1, 2, 0, 1, 1, 0, 1, 1, 0, 1, 0, 0, 0, 2, 2, 0, 0, 0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1
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OFFSET
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1,21
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LINKS
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EXAMPLE
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For n=5 we have (2^0) mod 5 = 1, (2^1) mod 5 = 2, (2^2) mod 5 = 4, (2^3) mod 5 = 3, (2^4) mod 5 = 1. Only for s=3 does (2^s) mod 5=s, so a(5)=1
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MATHEMATICA
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Table[Count[Range[0, n - 1], _?(Mod[2^#, n] == # &)], {n, 105}] (* Michael De Vlieger, Jun 19 2018 *)
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PROG
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(PARI) a(n) = sum(s=0, n-1, Mod(2, n)^s == s); \\ Michel Marcus, Jun 19 2018
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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Jonathan Ayres (jonathan.ayres(AT)btinternet.com), Oct 28 2001
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EXTENSIONS
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STATUS
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approved
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