A075706 Safe primes (A005385) (p and (p-1)/2 are primes) such that 8*p+1 (A023228) is also prime.
5, 11, 107, 179, 347, 479, 1187, 1307, 1367, 1487, 1619, 2027, 2207, 2447, 2999, 3119, 3467, 4007, 4079, 4139, 4799, 5087, 5807, 5927, 5939, 6827, 7079, 7247, 8699, 9587, 9839, 10607, 12107, 12539, 12659, 14207, 15299, 16139, 16187, 17027
Offset: 1
Keywords
Examples
11 is a prime, so is (11-1)/2=5 and also 8*11+1=89; 107 is a prime, (107-1)/2=53 and 8*107+1=857, ...
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
Programs
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Maple
ts_sg8_var_pras := proc(nmax) local i,tren,atek; tren := 0: for i from 1 to nmax do atek := numtheory[safeprime](i): if (atek > tren) then if (isprime(atek)='true' and isprime(6*atek+1)='true') then tren := atek: fi; fi; od; end: seq(ts_sg8_var_pras(i), i=1..3000);
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Mathematica
Select[Prime[Range[2000]],AllTrue[{(#-1)/2,8#+1},PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Jan 31 2020 *) -
PARI
forprime(p=3,20000,if(isprime((p-1)/2),if(isprime(8*p+1),print1(p","))))
Extensions
More terms from Ralf Stephan, Mar 19 2003