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A102998 Numbers n such that 4*10^n + 8*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
1, 4, 10, 12, 13, 40, 76, 123, 501, 648, 3541, 4002, 4228, 5271, 7432, 27306, 43402 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also numbers n such that (44*10^n-53)/9 is prime.

a(18) > 10^5. - Robert Price, Jun 01 2015

LINKS

Table of n, a(n) for n=1..17.

Makoto Kamada, Prime numbers of the form 488...883.

Index entries for primes involving repunits.

FORMULA

a(n) = A101735(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(44*10^n - 53)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101735.

Sequence in context: A078005 A092428 A170943 * A071179 A155475 A023693

Adjacent sequences:  A102995 A102996 A102997 * A102999 A103000 A103001

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 17 2005

EXTENSIONS

Addition of a(16) from Kamada data by Robert Price, Dec 12 2010

a(17) from Erik Branger, May 01 2013, submitted by Ray Chandler, Aug 16 2013

STATUS

approved

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Last modified September 17 11:03 EDT 2019. Contains 327129 sequences. (Running on oeis4.)