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A102955 Numbers n such that 2*10^n + 4*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n. 1
1, 15, 31, 73, 97, 499, 4207, 5902, 9568, 12142, 13048, 38341, 80167, 91903 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also numbers n such that (22*10^n+41)/9 is prime.

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

LINKS

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

Makoto Kamada, Prime numbers of the form 244...449.

Index entries for primes involving repunits.

FORMULA

a(n) = A101960(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(22*10^n + 41)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101960.

Sequence in context: A283122 A195046 A324631 * A041444 A041446 A042853

Adjacent sequences:  A102952 A102953 A102954 * A102956 A102957 A102958

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Dec 17 2004

EXTENSIONS

Addition of a(10)-a(11) from Kamada data by Robert Price, Dec 13 2010

a(12) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

a(13)-a(14) from Robert Price, Feb 05 2015

STATUS

approved

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Last modified November 11 18:50 EST 2019. Contains 329031 sequences. (Running on oeis4.)