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A099006
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Numbers n such that 2*10^n + 5*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.
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1
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2, 3, 26, 27, 45, 62, 147, 1277, 1665, 1979, 2970, 12773, 17702, 19128, 22206, 22386, 25053
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Also numbers n such that (23*10^n+13)/9 is prime.
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LINKS
| Makoto Kamada, Factorizations of 255...557.
Index entries for primes involving repunits.
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EXAMPLE
| n = 2, 3, 26, 27 are members since 257, 2557, 255555555555555555555555557 and
2555555555555555555555555557 are primes.
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MATHEMATICA
| Do[ If[ PrimeQ[(23*10^n + 13)/9], Print[n]], {n, 0, 10000}]
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CROSSREFS
| Sequence in context: A002748 A056004 A032812 * A041659 A042043 A178196
Adjacent sequences: A099003 A099004 A099005 * A099007 A099008 A099009
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KEYWORD
| more,nonn
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AUTHOR
| Julien Peter Benney (jpbenney(AT)ftml.net), Nov 07 2004
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EXTENSIONS
| a(8), a(9), a(10) & a(11) from Sam Handler (sam_5_5_5_0(AT)yahoo.com), Nov 17 2004
a(12)-a(17) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 14 2010
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