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A102983 Numbers n such that 4*10^n + R_n + 8 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
2, 5, 77, 206, 1871, 3887, 11582, 20234 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also numbers n such that (37*10^n+71)/9 is prime.

LINKS

Table of n, a(n) for n=1..8.

Makoto Kamada, Factorizations of 411...119.

Index entries for primes involving repunits.

MATHEMATICA

Do[ If[ PrimeQ[(37*10^n + 71)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Sequence in context: A128297 A183291 A216847 * A038583 A082080 A127997

Adjacent sequences:  A102980 A102981 A102982 * A102984 A102985 A102986

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Dec 21 2004

EXTENSIONS

Addition of a(7)-a(8) from Kamada data by Robert Price, Dec 13 2010

STATUS

approved

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Last modified December 20 12:05 EST 2014. Contains 252241 sequences.