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This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A060200 Number of Sophie Germain primes <= prime(2^n).

Original entry on oeis.org

2, 3, 4, 8, 12, 20, 32, 54, 94, 170, 297, 549, 1017, 1895, 3505, 6577, 12388, 23565, 44891, 85922, 164299, 314173, 602624, 1158231, 2232286
Offset: 1

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Author

Alexander D. Healy, Mar 19 2001

Keywords

Comments

Sophie Germain primes are primes p such that 2p+1 is also prime.

Examples

			The first four primes are 2, 3, 5 and 7. Three of these are Sophie Germain primes (since 2*2 + 1 = 5, 2*3 + 1 = 7 and 2*5 + 1 = 11 are prime, but 2*7 + = 15). Therefore the second value in the sequence is 3.

Crossrefs

Cf. A049040.

Programs

  • Mathematica
    << NumberTheory`NumberTheoryFunctions` cnt = 0; currentPrime = 1; For[ i = 1, i == i, i ++, currentPrime = NextPrime[ currentPrime ]; If[ PrimeQ[ 2*currentPrime + 1 ], cnt++ ]; If[ IntegerQ[ Log[ 2, i ] ], Print[ cnt ] ]; ]
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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