A102932 Numbers k such that 10^k + 3*R_k + 4 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

0, 1, 2, 4, 5, 12, 60, 109, 181, 245, 412, 887, 2477, 2918, 4622, 6240, 6253, 7684, 14630, 20932, 49801

Offset

1,3

Comments

Also numbers k such that (4*10^k + 11)/3 is prime.

a(22) > 2*10^5. - Robert Price, Feb 17 2018

Links

Table of n, a(n) for n=1..21.

Makoto Kamada, Prime numbers of the form 133...337.

Index entries for primes involving repunits.

Formula

a(n) = A102013(n-1) + 1.

Mathematica

Do[ If[ PrimeQ[(4*10^n + 11)/3], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A102013.

Sequence in context: A353850 A050599 A281643 * A128457 A139485 A079407

Adjacent sequences: A102929 A102930 A102931 * A102933 A102934 A102935

Keyword

more,nonn

Author

Robert G. Wilson v, Dec 16 2004

Extensions

Addition of a(19)-a(20) from Kamada data by Robert Price, Dec 10 2010

0 added by Arkadiusz Wesolowski, Mar 10 2011

a(21) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

Status

approved