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A067758
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Numbers k such that sigma(prime(k) - 1) == 0 (mod k).
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1
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1, 4, 9, 27, 42, 60, 64, 70, 78, 144, 168, 180, 216, 238, 260, 318, 558, 600, 672, 960, 1008, 1053, 1260, 1620, 1806, 2112, 3318, 3780, 4608, 5544, 12152, 40084, 40095, 41664, 47040, 48825, 49176, 51870, 59832, 60528, 71040, 99008, 100356, 113904, 132000, 159000
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OFFSET
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1,2
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COMMENTS
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There are 91 terms up to and including 10 million. - Harvey P. Dale, Oct 04 2016
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LINKS
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Amiram Eldar, Table of n, a(n) for n = 1..163 (terms 1..91 from Harvey P. Dale)
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MATHEMATICA
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Select[Range[120000], Divisible[DivisorSigma[1, Prime[#]-1], #]&] (* Harvey P. Dale, Oct 04 2016 *)
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PROG
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(PARI) for(k=1, 120000, if(sigma(prime(k)-1)%k==0, print1(k, ", ")))
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CROSSREFS
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Cf. A000203, A006093, A008332.
Sequence in context: A240042 A099615 A114618 * A304677 A214418 A164342
Adjacent sequences: A067755 A067756 A067757 * A067759 A067760 A067761
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KEYWORD
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nonn,changed
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AUTHOR
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Benoit Cloitre, Feb 05 2002
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EXTENSIONS
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More terms from Klaus Brockhaus, Feb 07 2002
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STATUS
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approved
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