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A274381 Safe primes p such that p + 24 is also a safe prime.

%I A274381 #40 Dec 31 2019 19:19:19
%S A274381 23,59,83,359,479,563,839,863,1283,2039,2879,2999,3779,4259,4679,5483,
%T A274381 7703,10079,12203,13103,23603,26903,27803,30323,31583,33623,35339,
%U A274381 41519,43403,44519,44939,53759,55079,57119,57899,58043,65123,66359,70139,70199,76379,77723,79943
%N A274381 Safe primes p such that p + 24 is also a safe prime.
%H A274381 John Cerkan, <a href="/A274381/b274381.txt">Table of n, a(n) for n = 1..10000</a>
%F A274381 { x | both x and x + 24 are safe primes }.
%e A274381 83 is a safe prime and so is 83 + 24 = 107.
%e A274381 4679 is a safe prime and so is 4679 + 24 = 4703.
%p A274381 A274381:=n->`if`(type((n-1)/2, prime) and isprime(n+24) and isprime(n) and type((n+23)/2, prime), n, NULL): seq(A274381(n), n=1..10^5); # _Wesley Ivan Hurt_, Jun 25 2016
%t A274381 Select[Prime@ Range[10^4], PrimeQ[(# - 1)/2] && PrimeQ[# + 24] && PrimeQ[(23 + #)/2] &] (* _Giovanni Resta_, Jun 23 2016 *)
%t A274381 Select[Prime[Range[8000]],AllTrue[{(#-1)/2,(#+23)/2,#+24},PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* _Harvey P. Dale_, Dec 31 2019 *)
%o A274381 (PARI) lista(nn) = forprime(p=3, nn, if (isprime((p-1)/2) && isprime(q=p+24) && isprime((q-1)/2), print1(p, ", "))); \\ _Michel Marcus_, Jun 23 2016
%Y A274381 Cf. A005385, A033560, A059323.
%K A274381 nonn
%O A274381 1,1
%A A274381 _Debapriyay Mukhopadhyay_, Jun 23 2016