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A102929 Numbers n such that 10^n + 2*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
0, 1, 3, 9, 48, 58, 153, 261, 876, 1179, 1596, 17715, 63718 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Also numbers n such that (11*10^n+7)/9 is prime.

a(14) > 10^5. - Robert Price, Nov 15 2014

LINKS

Table of n, a(n) for n=1..13.

Makoto Kamada, Prime numbers of the form 122...223.

Index entries for primes involving repunits

FORMULA

a(n) = A102009(n-1) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(11*10^n + 7)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A102009.

Sequence in context: A129432 A111551 A258481 * A105458 A306947 A183952

Adjacent sequences:  A102926 A102927 A102928 * A102930 A102931 A102932

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Dec 16 2004

EXTENSIONS

Addition of a(12) from Kamada data by Robert Price, Dec 13 2010

Inserted a(1)=0 by Robert Price, Nov 15 2014

a(13) from Kamada data by Robert Price, Nov 15 2014

STATUS

approved

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Last modified May 24 06:53 EDT 2019. Contains 323529 sequences. (Running on oeis4.)