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A103005 Numbers n such that 5*10^n + R_n + 2 is a prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
1, 3, 19, 109, 129, 280, 387, 447, 487, 1048, 3298, 3460, 9454, 26103, 61693, 66469 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also numbers n such that (46*10^n+17)/9 is a prime.

a(17) > 10^5. - Robert Price, Jun 20 2015

LINKS

Table of n, a(n) for n=1..16.

Makoto Kamada, Prime numbers of the form 511...113.

Index entries for primes involving repunits.

FORMULA

a(n) = A101570(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(46*10^n + 17)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101570.

Sequence in context: A240123 A130425 A334976 * A162354 A132959 A253811

Adjacent sequences:  A103002 A103003 A103004 * A103006 A103007 A103008

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 18 2005

EXTENSIONS

Addition of a(14) from Kamada data by Robert Price, Dec 12 2010

a(15)-a(16) from Robert Price, Jun 20 2015

STATUS

approved

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Last modified July 25 14:49 EDT 2021. Contains 346290 sequences. (Running on oeis4.)