A103016 - OEIS

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A103016

Numbers n such that 5*10^n + 4*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1

1, 3, 4, 6, 10, 21, 30, 72, 199, 208, 270, 396, 619, 759, 1077, 1383, 1566, 1960, 2653, 3504, 3786, 6085, 13110, 36448, 39582, 47989, 50998, 66729

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OFFSET

1,2

COMMENTS

Also numbers n such that (49*10^n+41)/9 is prime.

a(29) > 10^5. - Robert Price, Jul 21 2015

LINKS

Table of n, a(n) for n=1..28.

Makoto Kamada, Prime numbers of the form 544...449.

Index entries for primes involving repunits.

EXAMPLE

a(n) = A101581(n) + 1.

MATHEMATICA

Do[ If[ PrimeQ[(49*10^n + 41)/9], Print[n]], {n, 0, 10000}]

CROSSREFS

Cf. A002275, A101581.

Sequence in context: A052548 A232268 A103049 * A061032 A091424 A092839

Adjacent sequences: A103013 A103014 A103015 * A103017 A103018 A103019

KEYWORD

more,nonn

AUTHOR

Robert G. Wilson v, Jan 18 2005

EXTENSIONS

Addition of a(23) from Kamada data by Robert Price, Dec 09 2010

a(24)-a(26) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

a(27)-a(28) from Robert Price, Jul 21 2015

STATUS

approved