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A102962 Numbers n such that 2*10^n + 8*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
3, 6, 18, 69, 443, 449, 455, 2459, 4745, 7973, 14249, 31710 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also numbers n such that (26*10^n-17)/9 is prime.

a(13) > 10^5. - Robert Price, Mar 28 2015

LINKS

Table of n, a(n) for n=1..12.

Makoto Kamada, Prime numbers of the form 288...887.

Index entries for primes involving repunits.

FORMULA

a(n) = A101971(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(26*10^n - 17)/9], Print[n]], {n, 0, 10000}]

Select[Range[10000], PrimeQ[(26 10^# - 17) / 9] &] (* Vincenzo Librandi, Mar 29 2015 *)

PROG

(MAGMA) [n: n in [0..100] | IsPrime((26*10^n-17) div 9)]; // Vincenzo Librandi, Mar 29 2015

CROSSREFS

Cf. A002275, A101971.

Sequence in context: A215635 A215634 A178789 * A076510 A220816 A038060

Adjacent sequences:  A102959 A102960 A102961 * A102963 A102964 A102965

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Dec 17 2004

EXTENSIONS

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

a(12) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

STATUS

approved

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Last modified September 20 04:23 EDT 2020. Contains 337264 sequences. (Running on oeis4.)