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A103084 Numbers n such that 8*10^n + 5*R_n - 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
1, 2, 7, 44, 56, 338, 1211, 2693, 3536, 3917, 3974, 4046, 6961, 23771, 69656 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also numbers n such that (77*10^n-23)/9 is prime.

a(16) > 10^5. - Robert Price, Oct 22 2015

LINKS

Table of n, a(n) for n=1..15.

Makoto Kamada, Prime numbers of the form 855...553.

Index entries for primes involving repunits.

FORMULA

a(n) = A101071(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(77*10^n - 23)/9], Print[n]], {n, 0, 10000}]

PROG

(PARI) for(n=0, 1e5, if(isprime((77*10^n-23)/9), print1(n, ", "))) \\ Altug Alkan, Oct 22 2015

CROSSREFS

Cf. A002275, A101071.

Sequence in context: A212270 A270348 A270580 * A041507 A158107 A145073

Adjacent sequences:  A103081 A103082 A103083 * A103085 A103086 A103087

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 19 2005

EXTENSIONS

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

a(15) from Robert Price, Oct 22 2015

STATUS

approved

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Last modified March 5 11:57 EST 2021. Contains 341823 sequences. (Running on oeis4.)