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A297362
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Numbers n such that (2^ord(2, n) - 1)/n is prime, where ord(2, n) is the multiplicative order of 2 (mod n).
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0
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5, 9, 21, 23, 33, 47, 51, 73, 85, 89, 93, 129, 167, 217, 223, 263, 315, 341, 381, 585, 819, 1057, 1365, 3591, 3855, 4681, 4871, 5461, 6141, 6223, 6719, 7487, 8193, 11447, 13107, 13367, 13797, 14329, 16513, 18631, 21845, 24573, 25575, 26431, 33825, 37449
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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, 89, 31, 178481, 5, 7, 3, 23, 11, ...
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LINKS
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Table of n, a(n) for n=1..46.
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EXAMPLE
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5 is in the sequence since ord(2, 5) = 4 and (2^4 - 1)/5 = 3 is prime.
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MATHEMATICA
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aQ[n_] := PrimeQ[(2^MultiplicativeOrder[2, n] - 1)/n]; Select[Range[10000], aQ]
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CROSSREFS
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Cf. A002326, A165781.
Sequence in context: A273150 A273388 A273449 * A175364 A244642 A211424
Adjacent sequences: A297359 A297360 A297361 * A297363 A297364 A297365
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KEYWORD
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nonn
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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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