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A103087 Numbers n such that 8*10^n + 6*R_n - 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
0, 1, 2, 3, 13, 19, 62, 80, 126, 168, 195, 309, 410, 481, 608, 741, 879, 1176, 2688, 6236, 16294, 17317, 31574, 34861, 35392, 48726 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Also numbers n such that (26*10^n-11)/3 is prime.

a(27) > 10^5. - Robert Price, Oct 25 2015

LINKS

Table of n, a(n) for n=1..26.

Makoto Kamada, Prime numbers of the form 866...663.

Index entries for primes involving repunits.

FORMULA

a(n) = A101074(n-1) + 1, for n>1.

MATHEMATICA

Do[ If[ PrimeQ[(26*10^n - 11)/3], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101074.

Sequence in context: A194598 A080359 A193507 * A302485 A135118 A274905

Adjacent sequences:  A103084 A103085 A103086 * A103088 A103089 A103090

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 19 2005

EXTENSIONS

a(21)-a(22) from Kamada data by Robert Price, Dec 14 2010

a(23)-a(26) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

Inserted a(1)=0 by Robert Price, Oct 25 2015

STATUS

approved

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Last modified March 1 03:32 EST 2021. Contains 341732 sequences. (Running on oeis4.)