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A103035 Numbers n such that 6*10^n + 4*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
2, 5, 6, 11, 15, 69, 90, 134, 189, 245, 267, 270, 470, 1575, 2295, 2507, 3512, 3825, 6857, 11022, 11657, 17499 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

COMMENTS

Also numbers n such that (58*10^n-13)/9 is prime.

LINKS

Makoto Kamada, Factorizations of 644...443.

Index entries for primes involving repunits.

MATHEMATICA

Do[ If[ PrimeQ[(58*10^n - 13)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Sequence in context: A015613 A135013 A180323 * A088273 A049054 A135476

Adjacent sequences:  A103032 A103033 A103034 * A103036 A103037 A103038

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 18 2005

EXTENSIONS

a(20)-a(22) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 14 2010

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Last modified February 14 22:37 EST 2012. Contains 205679 sequences.