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A103083 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. +0
2
21, 27, 60, 471, 1074, 5781 (list; graph; listen)
OFFSET

1,1

COMMENT

Also numbers n such that (77*10^n-41)/9 is prime.

LINKS

Makoto Kamada, Factorizations of 855...551.

Index entries for primes involving repunits.

MATHEMATICA

Do[ If[ PrimeQ[(77*10^n - 41)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Sequence in context: A098898 A098768 A114168 this_sequence A120735 A009727 A048012

Adjacent sequences: A103080 A103081 A103082 this_sequence A103084 A103085 A103086

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 19 2005

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.


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