A158238 Primes p such that (p-7)/8 and 8p + 7 are both prime.

23, 47, 863, 1103, 1439, 1583, 1823, 2879, 3359, 4943, 5279, 6719, 7823, 8783, 9743, 11279, 11903, 12479, 13103, 16703, 18719, 19583, 20399, 20879, 21503, 23279, 23663, 25343, 26399, 27743, 29759, 33119, 35279, 38303, 39359, 39503, 41183

Offset: 1

Author

Zak Seidov, Mar 14 2009

Keywords

• nonn

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A023231 Numbers n such that n and 8n + 7 are both prime.

Programs

Mathematica

Select[Prime[Range[5000]],AllTrue[{(#-7)/8,8#+7},PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Mar 24 2015 *)

PARI

isok(p) = isprime(p) && isprime(8*p+7) && ((p % 8)==7) && isprime((p-7)/8); \\ Michel Marcus, Oct 16 2013

Formula

23, (23-7)/8=2, and 8*23+7=191 are all prime.