A102930 Numbers k such that 10^k + 2*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

1, 2, 4, 14, 25, 32, 56, 62, 811, 812, 1084, 2533, 11924, 49552

Offset

1,2

Comments

Also numbers k such that (11*10^k + 43)/9 is prime.

a(15) > 10^5. - Robert Price, Jan 16 2015

a(15) > 2*10^5. - Tyler Busby, Feb 01 2023

Links

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

Makoto Kamada, Prime numbers of the form 122...227.

Index entries for primes involving repunits.

Formula

a(n) = A102010(n) + 1.

Mathematica

Do[ If[ PrimeQ[(11*10^n + 43)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A102010.

Sequence in context: A350050 A096012 A261562 * A357996 A135113 A050564

Adjacent sequences: A102927 A102928 A102929 * A102931 A102932 A102933

Keyword

more,nonn

Author

Robert G. Wilson v, Dec 16 2004

Extensions

Addition of a(13) from Kamada data by Robert Price, Dec 12 2010

a(14) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

Status

approved