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A102999 Numbers n such that 4*10^n + 8*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
0, 1, 2, 7, 14, 25, 116, 427, 595, 637, 776, 1706, 16628, 55558 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Also numbers n such that (44*10^n-17)/9 is prime.

a(15) > 10^5. - Robert Price, Jun 05 2015

LINKS

Table of n, a(n) for n=1..14.

Makoto Kamada, Prime numbers of the form 488...887.

Index entries for primes involving repunits.

FORMULA

a(n) = A101736(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(44*10^n - 17)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101736.

Sequence in context: A249547 A088207 A194111 * A225277 A014112 A227016

Adjacent sequences:  A102996 A102997 A102998 * A103000 A103001 A103002

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 17 2005

EXTENSIONS

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

a(14) from Robert Price, Jun 05 2015

Prepended a(1) = 0 by Robert Price, Jun 05 2015

STATUS

approved

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Last modified September 20 16:46 EDT 2019. Contains 327242 sequences. (Running on oeis4.)