A049040 - OEIS

A049040

Number of Sophie Germain primes <= prime(10^n).

6, 26, 167, 1222, 9668, 82237, 711154, 6284076

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OFFSET

1,1

COMMENTS

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

LINKS

Table of n, a(n) for n=1..8.

Index entries for sequences related to numbers of primes in various ranges

EXAMPLE

The first 10 primes are 2,3,5,7,11,13,17,23,29 and 31. 6 of these are Sophie Germain primes, namely: 2,3,5,11,23 and 29.

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[ 10, i ] ], Print[ cnt ] ]; ]

CROSSREFS

Cf. A005384, A006988.

Sequence in context: A187458 A100308 A352694 * A103649 A053946 A211946

Adjacent sequences: A049037 A049038 A049039 * A049041 A049042 A049043

KEYWORD

nonn,more

AUTHOR

Dennis S. Kluk (mathemagician(AT)ameritech.net)

EXTENSIONS

More terms from Alexander D. Healy, Mar 19 2001

STATUS

approved