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A056694 Numbers n such that 80*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n. +0
3
0, 1, 2, 4, 7, 8, 14, 50, 70, 76, 223, 295, 314, 2089, 2905, 3394, 3881, 5113, 6055, 7253, 7994 (list; graph; listen)
OFFSET

1,3

COMMENT

Also numbers n such that (8*10^(n+1)-53)/9 is prime.

LINKS

Index entries for primes involving repunits

Makoto Kamada, Factorizations of 88...883.

MATHEMATICA

Do[ If[ PrimeQ[80*(10^n - 1)/9 + 3], Print[n]], {n, 0, 5000}]

CROSSREFS

Sequence in context: A018740 A018430 A018265 this_sequence A090606 A019539 A045594

Adjacent sequences: A056691 A056692 A056693 this_sequence A056695 A056696 A056697

KEYWORD

hard,nonn

AUTHOR

Robert G. Wilson v (rgwv(AT)rgwv.com), Aug 10 2000

EXTENSIONS

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008

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Last modified December 13 23:45 EST 2009. Contains 170824 sequences.


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