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A056722 Numbers k such that 8*10^k + R_k is prime, where R_k = 11...1 is the repunit (A002275) of length k. 1
2, 3, 26, 110, 141, 474, 902, 1746, 2997, 3627, 3788, 51162, 71670, 78576, 104942, 122592, 248145 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Also numbers k such that (73*10^k - 1)/9 is prime.
The next term is > 10000. - Hugo Pfoertner, Oct 21 2004
a(18) > 250000. - Robert Price, Jan 21 2015
LINKS
MATHEMATICA
Do[ If[ PrimeQ[ 8*10^n + (10^n-1)/9], Print[n]], {n, 0, 5000}]
CROSSREFS
Sequence in context: A042043 A178196 A258766 * A181225 A143876 A184506
KEYWORD
hard,nonn
AUTHOR
Robert G. Wilson v, Aug 11 2000
EXTENSIONS
a(12)-a(17) from Kamada data by Robert Price, Jan 21 2015
STATUS
approved

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Last modified May 22 06:48 EDT 2024. Contains 372743 sequences. (Running on oeis4.)