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A103804 Primes p such that both 2p +/- 21 are primes. 2

%I

%S 13,19,29,31,41,59,79,89,101,109,131,179,211,239,241,271,311,331,349,

%T 409,421,449,499,509,521,541,601,619,701,751,821,839,881,1009,1091,

%U 1181,1201,1319,1321,1399,1429,1459,1489,1531,1571,1619,1801,1949,1951

%N Primes p such that both 2p +/- 21 are primes.

%F p, 2p-21 and 2p+21 all are positive primes.

%t Select[Range[2000], PrimeQ[ # ] && PrimeQ[2# + 21] && PrimeQ[2# - 21] &]

%t Select[Prime[Range[4,500]],And@@PrimeQ[2#+{21,-21}]&] (* _Harvey P. Dale_, Dec 18 2012 *)

%Y Cf. A103802, A103803.

%K nonn

%O 1,1

%A _Zak Seidov_, Feb 16 2005

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Last modified May 11 12:47 EDT 2021. Contains 343791 sequences. (Running on oeis4.)