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A211397 Number of Sophie Germain primes less than 2^n. 2
0, 2, 3, 4, 6, 8, 11, 18, 26, 39, 62, 103, 170, 281, 474, 834, 1464, 2555, 4493, 8051, 14499, 26375, 48024, 88175, 161833, 297544, 549330, 1018008, 1893255, 3527324, 6588118, 12334363, 23140567, 43497488, 81930886, 154587025, 292149120 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..37.

Paul D. Beale, A new class of scalable parallel pseudorandom number generators based on Pohlig-Hellman exponentiation ciphers, arXiv preprint arXiv:1411.2484, 2014-2015.

Paul D. Beale, Jetanat Datephanyawat, Class of scalable parallel and vectorizable pseudorandom number generators based on non-cryptographic RSA exponentiation ciphers, arXiv:1811.11629 [cs.CR], 2018.

MATHEMATICA

nmax = 37; stable = Table[0, {nmax}];

Do[s = 0;

  Do[If[And[PrimeQ[i], PrimeQ[2 i + 1]], s++], {i, 1, 2^n - 1}];

  Print[n, " ", s]; stable[[n]] = s, {n, 1, nmax}];

stable (* Paul D. Beale, Sep 19 2014 *)

PROG

(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}

CROSSREFS

Cf. A211395, A005385.

Sequence in context: A054782 A261082 A271487 * A173542 A323383 A085113

Adjacent sequences:  A211394 A211395 A211396 * A211398 A211399 A211400

KEYWORD

nonn

AUTHOR

Michael B. Porter, Feb 08 2013

EXTENSIONS

a(30)-a(37) from Paul D. Beale, Sep 19 2014

STATUS

approved

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Last modified November 19 00:12 EST 2019. Contains 329310 sequences. (Running on oeis4.)