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A076495
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Smallest x such that Mod(sigma(x),x) = n, or 0 if no such x exists.
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3
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2, 20, 4, 9, 0, 25, 8, 10, 15, 14, 21, 24, 27, 22, 16, 26, 39, 208, 36, 34, 51, 38, 57, 112, 95, 46, 69, 48, 115, 841, 32, 58, 45, 62, 93, 660, 155, 1369, 162, 44, 63, 1681, 50, 82, 123, 52, 129, 60, 75, 94, 72, 352, 235, 90, 329, 84, 99, 68, 265, 96, 371, 118, 64, 76
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OFFSET
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1,1
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COMMENTS
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The 0 entries are at present only conjectures.
For n <= 1000, a(5) and a(898) are the only terms not found using x <= 10^11. - Donovan Johnson, Sep 20 2012
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LINKS
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Donovan Johnson, Table of n, a(n) for n = 1..1000
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EXAMPLE
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n=1: solution = smallest prime. n=3: Mod(sigma(4),4) = Mod(7,4) = 3. n=5: Very difficult case, no solution below 10^7.
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MATHEMATICA
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f[x_] := s=Mod[DivisorSigma[1, n], n]; t=Table[0, {256}]; Do[s=f[n]; If[s<257&&t[[s]]==0, t[[s]]=n], {n, 1, 10000000}]; t
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CROSSREFS
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Cf. A045768, A045769, A045770.
Sequence in context: A082259 A077339 A077341 * A058403 A083297 A221921
Adjacent sequences: A076492 A076493 A076494 * A076496 A076497 A076498
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Oct 21 2002
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STATUS
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approved
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