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A102968 Numbers n such that 3*10^n + 2*R_n + 7 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
3, 5, 9, 12, 27, 51, 53, 147, 155, 257, 519, 603, 2885, 9509, 10524, 19650 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

COMMENTS

Also numbers n such that (29*10^n+61)/9 is prime.

LINKS

Makoto Kamada, Factorizations of 322...229.

Index entries for primes involving repunits.

MATHEMATICA

Do[ If[ PrimeQ[(29*10^n+61)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Sequence in context: A059093 A084593 A161866 * A180341 A177078 A187906

Adjacent sequences:  A102965 A102966 A102967 * A102969 A102970 A102971

KEYWORD

more,nonn

AUTHOR

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

EXTENSIONS

A(13) from Julien Peter Benney (jpbenney(AT)ftml.net), Jan 16 2005

A(14) from Robert G. Wilson v (rgwv(AT)rgwv.com), Jan 17 2005

Addition of a(15)-a(16) from Kamada data by Robert Price (pamandbobprice(AT)yahoo.com), Dec 12 2010

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Last modified February 15 03:33 EST 2012. Contains 205694 sequences.