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A000353
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Primes == 7, 19, 23 (mod 40) such that (p-1)/2 is also prime.
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3
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7, 23, 47, 59, 167, 179, 263, 383, 503, 863, 887, 983, 1019, 1367, 1487, 1619, 1823, 2063, 2099, 2207, 2447, 2459, 2579, 2819, 2903, 3023, 3167, 3623, 3779, 3863, 4007, 4127, 4139, 4259, 4703, 5087, 5099, 5807, 5927, 5939, 6047, 6659, 6779, 6899, 6983
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OFFSET
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1,1
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COMMENTS
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a(n) = 2*A000355(n)+1; the decimal expansion of 1/a(n) will produce a stream of a(n)-1 pseudo-random digits. -Reinhard Zumkeller, Feb 10 2009
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REFERENCES
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R. A. J. Matthews, Maximally periodic reciprocals, Bull. Institute of Mathematics and Its Applications, vol. 28, p. 147-148, 1992.
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LINKS
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R. Zumkeller, Table of n, a(n) for n = 1..1000
Wikipedia, Sophie Germain prime
Index entries for sequences related to decimal expansion of 1/n.
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MATHEMATICA
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Select[Prime[Range[1000]], MatchQ[Mod[#, 40], 7|19|23] && PrimeQ[(#-1)/2]&] (* Jean-François Alcover, Feb 07 2016 *)
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PROG
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(PARI) is(n)=my(k=n%40); (k==7||k==19||k==23) && isprime(n\2) && isprime(n) \\ Charles R Greathouse IV, Nov 20 2014
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CROSSREFS
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Subset of A005385.
Subsequence of A001913, A006883.
Sequence in context: A319050 A031371 A176557 * A097149 A185007 A308732
Adjacent sequences: A000350 A000351 A000352 * A000354 A000355 A000356
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KEYWORD
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nonn
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AUTHOR
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R. A. J. Matthews [ 100265.3005(AT)compuserve.com ]
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EXTENSIONS
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More terms from Reinhard Zumkeller, Feb 10 2009
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STATUS
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approved
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