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%I #28 Jan 23 2019 03:06:31
%S 0,2,3,4,6,8,11,18,26,39,62,103,170,281,474,834,1464,2555,4493,8051,
%T 14499,26375,48024,88175,161833,297544,549330,1018008,1893255,3527324,
%U 6588118,12334363,23140567,43497488,81930886,154587025,292149120
%N Number of Sophie Germain primes less than 2^n.
%H Paul D. Beale, <a href="http://arxiv.org/abs/1411.2484">A new class of scalable parallel pseudorandom number generators based on Pohlig-Hellman exponentiation ciphers</a>, arXiv preprint arXiv:1411.2484, 2014-2015.
%H Paul D. Beale, Jetanat Datephanyawat, <a href="https://arxiv.org/abs/1811.11629">Class of scalable parallel and vectorizable pseudorandom number generators based on non-cryptographic RSA exponentiation ciphers</a>, arXiv:1811.11629 [cs.CR], 2018.
%t nmax = 37; stable = Table[0, {nmax}];
%t Do[s = 0;
%t Do[If[And[PrimeQ[i], PrimeQ[2 i + 1]], s++], {i, 1, 2^n - 1}];
%t Print[n, " ", s]; stable[[n]] = s, {n, 1, nmax}];
%t stable (* _Paul D. Beale_, Sep 19 2014 *)
%o (PARI) a211397(n) = {local(r,i); r=0; for(i=1, 2^n-1, if(isprime(i)&&isprime(2*i+1), r=r+1)); r}
%Y Cf. A211395, A005385.
%K nonn
%O 1,2
%A _Michael B. Porter_, Feb 08 2013
%E a(30)-a(37) from _Paul D. Beale_, Sep 19 2014
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