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A297360
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Numbers k such that (2^lambda(k) - 1)/k is prime, where lambda(k) is the Carmichael lambda function (A002322).
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0
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OFFSET
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1,1
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COMMENTS
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The corresponding primes are 3, 7, 3, 31, 257, 13, 7, 5, 3, 73, ...
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LINKS
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Table of n, a(n) for n=1..10.
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EXAMPLE
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5 is in the sequence since lambda(5) = 4 and (2^4 - 1)/5 = 3 is prime.
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MATHEMATICA
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aQ[n_] := PrimeQ[(2^CarmichaelLambda[n]-1)/n]; a={}; Do[If[aQ[k], AppendTo[a, k]], {k, 1, 4000, 2}]; a
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PROG
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(PARI) isok(n) = (denominator(p=(2^lcm(znstar(n)[2])-1)/n)==1) && isprime(p); \\ Michel Marcus, Dec 29 2017
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CROSSREFS
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Cf. A002322.
Sequence in context: A146867 A068481 A146827 * A216414 A147018 A081883
Adjacent sequences: A297357 A297358 A297359 * A297361 A297362 A297363
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KEYWORD
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nonn,more
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AUTHOR
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Amiram Eldar, Dec 29 2017
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STATUS
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approved
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