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A270573
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Let c be the n-th composite number. a(n) is the number of composites d < c such that c^(d-1) == 1 (mod d) and d^(c-1) == 1 (mod c).
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3
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0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 2, 0, 1, 0, 0, 0, 1, 0, 2, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 3, 0, 1, 0, 0, 6, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 1, 1, 0, 1, 0, 1, 0
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OFFSET
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1,38
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LINKS
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PROG
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(PARI) forcomposite(c=1, 100, my(i=0); forcomposite(d=1, c-1, if(Mod(c, d)^(d-1)==1 && Mod(d, c)^(c-1)==1, i++)); print1(i, ", "))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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