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A097970
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Numbers n such that 7*10^n + 3 is prime.
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1
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1, 4, 6, 16, 22, 39, 103, 163, 240, 1048, 1974, 2559, 5880, 14436, 28338, 32796, 38079, 56779, 91215
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OFFSET
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1,2
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LINKS
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Table of n, a(n) for n=1..19.
Makoto Kamada, Factorizations of 700...003.
Sabin Tabirca and Kieran Reynolds, Lacunary Prime Numbers.
Index entries for primes involving repunits.
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EXAMPLE
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For n = 1 we have 7*10^1+3 =7*10+3 = 73, which is prime.
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MATHEMATICA
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Do[ If[ PrimeQ[ 7*10^n + 3], Print[ n ]], {n, 0, 10000}] (from Robert G. Wilson v Jan 19 2005)
Flatten[Position[Table[7 10^n+3, {n, 100000}], _?PrimeQ]] (* From Harvey P. Dale, Nov 01 2011 *)
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CROSSREFS
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Sequence in context: A117988 A120542 A132344 * A044858 A120375 A025618
Adjacent sequences: A097967 A097968 A097969 * A097971 A097972 A097973
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KEYWORD
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more,nonn
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AUTHOR
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Julien Peter Benney (jpbenney(AT)ftml.net), Sep 07 2004
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EXTENSIONS
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a(10)-a(13) from Robert G. Wilson v, Jan 19 2005
a(14)-a(19) from Kamada data by Robert Price, Dec 14 2010
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STATUS
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approved
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