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A103802 Primes p such that 2p - 9 and 2p + 9 are both primes. 4

%I

%S 7,11,19,31,59,61,79,101,151,179,229,311,359,389,409,521,709,719,751,

%T 809,971,1039,1061,1151,1171,1201,1361,1459,1481,1669,1699,1811,1949,

%U 1999,2131,2341,2371,2411,2609,2671,2711,2791,2851,3019,3041,3061,3119

%N Primes p such that 2p - 9 and 2p + 9 are both primes.

%F p, 2p-9 and 2p+9 all are positive and are primes (hence we omit p=2).

%t Select[Range[7,6000], PrimeQ[ # ] && PrimeQ[2# + 9] && PrimeQ[2# - 9] &]

%t okQ[n_]:=Module[{c=2n},PrimeQ[c+9]&&PrimeQ[c-9]]; Select[Prime[ Range[5,500]],okQ] (* _Harvey P. Dale_, Apr 25 2011 *)

%o (MAGMA) [p: p in PrimesUpTo(3200)| IsPrime(2*p+9) and IsPrime(2*p-9) ]; // _Vincenzo Librandi_, Jan 28 2011

%K nonn

%O 1,1

%A _Zak Seidov_, Feb 16 2005

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Last modified January 26 05:10 EST 2020. Contains 331273 sequences. (Running on oeis4.)