A093405 - OEIS

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A093405

Primes of the form 80*R_k + 9, where R_k is the repunit (A002275) of length k.

0

89, 88888888888889, 88888888888888889, 88888888888888888888888888888888889

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Primes of the form (8*10^k + 1)/9. - Vincenzo Librandi, Jul 17 2012

LINKS

Table of n, a(n) for n=1..4.

Makoto Kamada, Prime numbers of the form 88...889.

Index entries for primes involving repunits

MATHEMATICA

Select[Table[(8*10^n+1)/9, {n, 1, 200}], PrimeQ] (* Vincenzo Librandi, Jul 17 2012 *)

Select[Table[FromDigits[PadLeft[{9}, n, 8]], {n, 100}], PrimeQ] (* Harvey P. Dale, Dec 15 2023 *)

CROSSREFS

Cf. A056663 (corresponding k).

Sequence in context: A072314 A087538 A087341 * A348166 A221307 A058631

Adjacent sequences: A093402 A093403 A093404 * A093406 A093407 A093408

KEYWORD

nonn

AUTHOR

Rick L. Shepherd, Mar 28 2004

STATUS

approved