login
Smaller term of closest safe prime pairs.
4

%I #12 Sep 08 2022 08:45:02

%S 11,47,167,347,467,1307,2027,2447,4127,4787,5087,5387,5927,12527,

%T 12647,15287,18947,28307,39107,39827,41507,44687,51827,63587,64007,

%U 71987,73847,76367,76907,78467,79967,83207,118787,121547,143687,164987

%N Smaller term of closest safe prime pairs.

%H Amiram Eldar, <a href="/A059323/b059323.txt">Table of n, a(n) for n = 1..10000</a>

%F {x| both x and x+12 are safe primes}; Intersection(12+A005385, primes)

%e 11 and 23 are consecutive safe primes but not consecutive primes; 467 and 479 are consecutive safe primes and consecutive primes as well. Both 11 and 467 are here.

%t seqQ[n_] := And @@ PrimeQ[{n, n+12, (n-1)/2, (n+11)/2}]; Select[Range[165000], seqQ] (* _Amiram Eldar_, Jan 13 2020 *)

%o (Magma) [p:p in PrimesUpTo(165000)| IsPrime(p+12) and IsPrime((p-1) div 2) and IsPrime( (p+11) div 2)]; // _Marius A. Burtea_, Jan 13 2020

%Y Cf. A005383, A033299.

%K nonn

%O 1,1

%A _Labos Elemer_, Jan 26 2001

%E Offset corrected by _Amiram Eldar_, Jan 13 2020