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%I #30 Feb 04 2024 01:10:34
%S 2,5,11,17,29,71,101,107,131,137,149,179,239,269,347,401,431,449,479,
%T 491,509,557,599,617,659,677,761,809,821,857,929,941,947,977,1151,
%U 1187,1229,1289,1307,1361,1367,1409,1487,1559,1571,1601,1619,1667,1697,1811,1871
%N Numbers k such that k and 8*k + 1 are both prime.
%H Vincenzo Librandi, <a href="/A023228/b023228.txt">Table of n, a(n) for n = 1..1000</a>
%H Samuel S. Wagstaff, Jr., <a href="https://cs.uwaterloo.ca/journals/JIS/VOL24/Wagstaff/wag4.html">Sum of Reciprocals of Germain Primes</a>, Journal of Integer Sequences, Vol. 24, No. 2 (2021), Article 21.9.5.
%F Sum_{n>=1} 1/a(n) is in the interval (1.151956749, 1.4207187) (Wagstaff, 2021). - _Amiram Eldar_, Nov 04 2021
%t Select[Prime[Range[2000]], PrimeQ[8# + 1]&] (* _Vincenzo Librandi_, Feb 02 2014 *)
%o (Magma) [ p: p in PrimesUpTo(1900) | IsPrime(8*p+1) ]; // _Klaus Brockhaus_, Dec 21 2008
%o (PARI) list(lim)=my(v=List()); forprime(p=2,lim, if(isprime(8*p+1), listput(v,p))); Vec(v) \\ _Charles R Greathouse IV_, Oct 20 2021
%Y Cf. A007519 (primes of form 8n+1), A005123 ((( primes == 1 mod 8 ) - 1)/8). - _Klaus Brockhaus_, Dec 21 2008
%K nonn,easy
%O 1,1
%A _David W. Wilson_
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