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A206714
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Number of solutions (n,k) of s(k)=s(n) (mod n), where 1<=k<n and s(k)=2^(k-1).
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2
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0, 1, 1, 1, 2, 2, 4, 1, 2, 1, 4, 1, 4, 3, 11, 2, 2, 1, 4, 3, 2, 2, 10, 1, 2, 1, 8, 1, 7, 6, 26, 3, 4, 2, 5, 1, 2, 3, 9, 2, 6, 3, 4, 3, 4, 2, 21, 2, 2, 6, 4, 1, 2, 2, 17, 3, 2, 1, 14, 1, 12, 10, 57, 5, 6, 1, 8, 3, 5, 2, 11, 8, 2, 3, 4, 2, 6, 2, 18, 1, 4, 1, 13, 10, 6, 3, 8, 8, 7, 7, 8, 9, 4
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OFFSET
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2,5
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LINKS
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EXAMPLE
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2^6=64; the numbers 64-s(j) are 63,62,60,56,48,32, of which two are multiples of 6, so that a(6)=2.
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MATHEMATICA
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s[k_] := 2^(k - 1);
f[n_, k_] := If[Mod[s[n] - s[k], n] == 0, 1, 0];
t[n_] := Flatten[Table[f[n, k], {k, 1, n - 1}]]
a[n_] := Count[Flatten[t[n]], 1]
Table[a[n], {n, 2, 120}] (* A206714 *)
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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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