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A049040
Number of Sophie Germain primes <= prime(10^n).
1
6, 26, 167, 1222, 9668, 82237, 711154, 6284076
OFFSET
1,1
COMMENTS
Sophie Germain primes are primes p such that 2p+1 is also prime.
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
Sequence in context: A187458 A100308 A352694 * A103649 A053946 A211946
KEYWORD
nonn,more
AUTHOR
Dennis S. Kluk (mathemagician(AT)ameritech.net)
EXTENSIONS
More terms from Alexander D. Healy, Mar 19 2001
STATUS
approved