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A102963 Numbers n such that 2*10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
0, 1, 7, 8, 11, 14, 19, 32, 41, 53, 61, 133, 157, 239, 1237, 30254, 34423, 139289 (list; graph; refs; listen; history; internal format)
OFFSET

1,3

COMMENTS

Also numbers n such that (26*10^n+1)/9 is prime.

LINKS

Makoto Kamada, Factorizations of 288...889.

Index entries for primes involving repunits.

MATHEMATICA

Do[ If[ PrimeQ[(26*10^n + 1)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Sequence in context: A195240 A090385 A145826 * A117619 A098731 A105740

Adjacent sequences:  A102960 A102961 A102962 * A102964 A102965 A102966

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 17 2004

EXTENSIONS

a(16)-a(18) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 14 2010

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Last modified February 17 10:05 EST 2012. Contains 206009 sequences.