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A103086 Numbers n such that 8*10^n + 5*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
1, 2, 8, 17, 19, 25, 40, 49, 58, 59, 92, 113, 296, 637, 1856, 2515, 3593, 6991, 11840, 86072, 93508 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also numbers n such that (77*10^n+31)/9 is prime.

a(22) > 10^5. - Robert Price, Oct 26 2015

LINKS

Table of n, a(n) for n=1..21.

Makoto Kamada, Prime numbers of the form 855...559.

Index entries for primes involving repunits.

FORMULA

a(n) = A101073(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(77*10^n + 31)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101073.

Sequence in context: A009662 A279243 A162218 * A192155 A131362 A284395

Adjacent sequences:  A103083 A103084 A103085 * A103087 A103088 A103089

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 19 2005

EXTENSIONS

a(19) from Kamada data by Robert Price, Dec 14 2010

a(20)-a(21) from Robert Price, Oct 26 2015

STATUS

approved

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Last modified May 26 18:08 EDT 2020. Contains 334630 sequences. (Running on oeis4.)