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A165318
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Primes p where the number of divisors of p-1 is a power of 2.
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3
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2, 3, 7, 11, 23, 31, 41, 43, 47, 59, 67, 71, 79, 83, 89, 103, 107, 131, 137, 139, 167, 179, 191, 211, 223, 227, 233, 239, 251, 263, 271, 281, 283, 311, 313, 331, 347, 359, 367, 379, 383, 409, 419, 431, 439, 443, 457, 463, 467, 479, 499, 503, 521, 547, 563, 569
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OFFSET
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1,1
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LINKS
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MAPLE
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isA000079 := proc(n) RETURN( n=1 or numtheory[factorset](n) = {2}) ; end: A165318 := proc(n) if n = 1 then 2; else p := nextprime(procname(n-1)) ; while not isA000079(numtheory[tau](p-1)) do p := nextprime(p) ; od; p ; fi; end: seq(A165318(n), n=1..90) ; # R. J. Mathar, Sep 18 2009
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MATHEMATICA
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Select[Prime[Range[200]], IntegerQ[Log[2, DivisorSigma[0, #-1]]]&] (* Harvey P. Dale, Oct 14 2018 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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