A103015 Numbers n such that 5*10^n + 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

2, 6, 8, 18, 53, 68, 242, 276, 320, 564, 620, 1782, 2340, 2454, 5765, 15530, 15605, 22938

Offset

1,1

Comments

Also numbers n such that (49*10^n+23)/9 is prime.

a(19) > 10^5. - Robert Price, Jul 29 2015

Links

Table of n, a(n) for n=1..18.

Makoto Kamada, Prime numbers of the form 544...447.

Index entries for primes involving repunits.

Formula

a(n) = A101580(n) + 1.

Mathematica

Do[ If[ PrimeQ[(49*10^n + 23)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101580.

Sequence in context: A163911 A301799 A077638 * A323859 A365918 A098092

Adjacent sequences: A103012 A103013 A103014 * A103016 A103017 A103018

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

a(16)-a(18) from Kamada data by Robert Price, Dec 14 2010

Status

approved