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A063911 Numbers n such that n and 2n-9 are primes. 2

%I

%S 7,11,13,19,23,31,41,53,59,61,73,79,83,101,103,139,151,163,173,179,

%T 181,191,199,229,233,283,293,311,313,331,359,383,389,409,419,431,433,

%U 443,503,509,521,563,569,601,613,619,643,653,691,709,719

%N Numbers n such that n and 2n-9 are primes.

%H Harry J. Smith, <a href="/A063911/b063911.txt">Table of n, a(n) for n = 1..1000</a>

%t Select[Prime[Range[3, 2000]], PrimeQ[2 # - 9]&] (* _Vincenzo Librandi_, Feb 02 2014

%o (PARI) { n=0; p=1; for (m=1, 10^9, p=nextprime(p+1); if (isprime(2*p - 9), write("b063911.txt", n++, " ", p); if (n==1000, break)) ) } \\ _Harry J. Smith_, Sep 02 2009

%o (MAGMA) [n: n in [4..2000] | IsPrime(n) and IsPrime(2*n-9)]; // _Vincenzo Librandi_, Feb 02 2014

%K nonn,easy

%O 1,1

%A _N. J. A. Sloane_, Aug 31 2001

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Last modified September 15 14:38 EDT 2019. Contains 327078 sequences. (Running on oeis4.)