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A103063 Numbers n such that 7*10^n + 6*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
1, 2, 6, 25, 69, 253, 300, 384, 434, 721, 822, 883, 2192, 2649, 3441, 3445, 8028, 11655 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also numbers n such that (23*10^n-17)/3 is prime.

LINKS

Table of n, a(n) for n=1..18.

Makoto Kamada, Factorizations of 766...661.

Index entries for primes involving repunits.

MATHEMATICA

Do[ If[ PrimeQ[(23*10^n - 17)/3], Print[n]], {n, 0, 10000}]

CROSSREFS

Sequence in context: A086591 A173609 A073545 * A220191 A030228 A066317

Adjacent sequences:  A103060 A103061 A103062 * A103064 A103065 A103066

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 19 2005

EXTENSIONS

a(18) from Kamada data by Robert Price, Dec 14 2010

STATUS

approved

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Last modified October 30 09:47 EDT 2014. Contains 248797 sequences.