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A102954 Numbers n such that 2*10^n + 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n. +0
2
3, 9, 15, 21, 27, 87, 180, 1941, 3960, 4995, 8577 (list; graph; listen)
OFFSET

1,1

COMMENT

Also numbers n such that (22*10^n+23)/9 is prime.

LINKS

Makoto Kamada, Factorizations of 244...447.

Index entries for primes involving repunits.

MATHEMATICA

Do[ If[ PrimeQ[(22*10^n + 23)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Adjacent sequences: A102951 A102952 A102953 this_sequence A102955 A102956 A102957

Sequence in context: A032676 A016945 A110108 this_sequence A067201 A071526 A114271

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v (rgwv(AT)rgwv.com), Dec 17 2004

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Last modified October 6 12:54 EDT 2008. Contains 144667 sequences.


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