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A049040
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Number of Sophie Germain primes <= Prime[ 10^n ].
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1
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OFFSET
| 1,1
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COMMENTS
| Sophie Germain primes are primes p such that 2p+1 is also prime.
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LINKS
| Index entries for sequences related to numbers of primes in various ranges
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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.
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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 ] ]; ]
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CROSSREFS
| Sequence in context: A144037 A187458 A100308 * A103649 A053946 A027283
Adjacent sequences: A049037 A049038 A049039 * A049041 A049042 A049043
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KEYWORD
| nonn
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AUTHOR
| Dennis S. Kluk (mathemagician(AT)ameritech.net)
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EXTENSIONS
| More terms from Alex Healy (ahealy(AT)post.harvard.edu), Mar 19 2001
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