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A102977 Numbers n such that 3*10^n + 7*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
0, 2, 3, 5, 6, 20, 776, 1185, 3164, 4212, 10733, 21726, 38235 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also numbers n such that (34*10^n+11)/9 is prime.

a(14) > 10^5. - Robert Price, May 08 2015

LINKS

Table of n, a(n) for n=1..13.

Makoto Kamada, Prime numbers of the form 377...779.

Index entries for primes involving repunits.

FORMULA

a(n) = A101843(n-1) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(34*10^n + 11)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101843.

Sequence in context: A109628 A192367 A227230 * A238335 A131599 A263650

Adjacent sequences:  A102974 A102975 A102976 * A102978 A102979 A102980

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Dec 17 2004

EXTENSIONS

Addition of a(11)-a(12) from Kamada data by Robert Price, Dec 13 2010

a(13) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

STATUS

approved

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Last modified August 20 06:04 EDT 2019. Contains 326139 sequences. (Running on oeis4.)