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 A000353 Primes == 7, 19, 23 (mod 40) such that (p-1)/2 is also prime. 2
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 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 REFERENCES R. A. J. Matthews, Maximally periodic reciprocals, Bull. Institute of Mathematics and Its Applications, vol. 28, p. 147-148, 1992. LINKS R. Zumkeller, Table of n, a(n) for n = 1..1000 Wikipedia, Sophie Germain prime MATHEMATICA Select[Prime[Range[1000]], MatchQ[Mod[#, 40], 7|19|23] && PrimeQ[(#-1)/2]&] (* Jean-François Alcover, Feb 07 2016 *) PROG (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 CROSSREFS Subset of A005385. Subsequence of A001913, A006883. Sequence in context: A031095 A031371 A176557 * A097149 A185007 A139035 Adjacent sequences:  A000350 A000351 A000352 * A000354 A000355 A000356 KEYWORD nonn AUTHOR R. A. J. Matthews [ 100265.3005(AT)compuserve.com ] EXTENSIONS More terms from Reinhard Zumkeller, Feb 10 2009 STATUS approved

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