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 A164566 Primes p such that 7*p-6 and 7*p+6 are also prime numbers. 4
 5, 11, 19, 31, 41, 61, 71, 109, 151, 211, 229, 269, 379, 419, 431, 439, 479, 619, 641, 709, 739, 809, 839, 971, 1009, 1069, 1229, 1259, 1319, 1361, 1439, 1451, 1499, 1531, 1579, 1669, 1801, 1879, 1889, 2011, 2111, 2239, 2269, 2381, 2411, 2551, 2579, 2591 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes of the form A087681(k)/7, any index k. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 FORMULA A136052 INTERSECT A023225. [R. J. Mathar, Aug 20 2009] EXAMPLE For p=5, both 7*5-6=29 and 7*5+6=41 are prime, for p=11, both 7*11-6=71 and 7*11+6=83 are prime. MATHEMATICA lst={}; Do[p=Prime[n]; If[PrimeQ[7*p-6]&&PrimeQ[7*p+6], AppendTo[lst, p]], {n, 6!}]; lst Select[Prime[Range[700]], And @@ PrimeQ/@{7 # + 6, 7 # - 6}&] (* Vincenzo Librandi, Apr 09 2013 *) PROG (MAGMA) [p: p in PrimesUpTo(3000) | IsPrime(7*p-6) and IsPrime(7*p+6)]; // Vincenzo Librandi, Apr 09 2013 (PARI) is(n)=isprime(n) && isprime(7*n-6) && isprime(7*n+6) \\ Charles R Greathouse IV, Mar 28 2017 CROSSREFS Cf. A106015, A125272, A127430, A046133, A087681, A136052, A023225. Sequence in context: A191032 A003147 A106068 * A075322 A079850 A065995 Adjacent sequences:  A164563 A164564 A164565 * A164567 A164568 A164569 KEYWORD nonn,easy AUTHOR Vladimir Joseph Stephan Orlovsky, Aug 16 2009 EXTENSIONS Examples rephrased by R. J. Mathar, Aug 20 2009 STATUS approved

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