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Search: id:A152008
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| A152008 |
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Primes which are divisors of numbers of the form (2^EulerPhi[3^k]-1)/3^k |
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+0
2
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| 7, 19, 73, 163, 487, 1459, 2593, 17497, 39367, 52489, 71119, 80191, 87211, 97687, 135433, 139483, 209953, 262657, 379081
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The primes in this sequence have the property that with the exception of 7 they are congruent to 1 mod 18 and with the exception of 7, 19, 73 are congruent to 1 mod 54.
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MATHEMATICA
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a = {}; Do[k = ((2^EulerPhi[3^(w + 1)] - 1)/3^(w + 1))/((2^EulerPhi[3^w] - 1)/3^w); Do[If[Mod[k, Prime[n]] == 0, AppendTo[a, Prime[n]]; Print[Prime[n]]], {n, PrimePi[2], PrimePi[379081]}], {w, 1, 20}]; Union[a] (*Artur Jasinski*)
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CROSSREFS
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Cf. A008776, A152007
Sequence in context: A155296 A155463 A005516 this_sequence A002533 A111011 A144723
Adjacent sequences: A152005 A152006 A152007 this_sequence A152009 A152010 A152011
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KEYWORD
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hard,nonn
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AUTHOR
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Artur Jasinski (grafix(AT)csl.pl), Nov 19 2008
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EXTENSIONS
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Edited by N. J. A. Sloane (njas(AT)research.att.com), Nov 26 2008
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