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A307176
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Number of Sophie Germain primes of the form 4k + 1 less than 10^n.
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1
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1, 5, 17, 89, 589, 3833, 27940, 211439, 1653257, 13283194, 109058142, 911411528, 7731354496
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OFFSET
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1,2
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COMMENTS
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Sophie Germain primes can alternatively be Lucasian primes, primes of the form 4k + 1, or, the individual prime 2.
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LINKS
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FORMULA
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a(n) <= A091098(n) (with equality for n = 1).
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EXAMPLE
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There are five Sophie Germain Primes of the form 4k + 1 below 10^2: {5, 29, 41, 53, 89}, therefore a(2) = 5.
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MATHEMATICA
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nonLucSophies = Select[4Range[2500000] + 1, PrimeQ[#] && PrimeQ[2# + 1] &]; Table[Length[Select[nonLucSophies, # < 10^n &]], {n, 0, 7}]
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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