A103010 Numbers k such that 5*10^k + 2*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

3, 5, 33, 48, 59, 60, 74, 126, 177, 228, 638, 1304, 1644, 2435, 4374, 8750, 15114, 16853, 30353, 30545, 36236

Offset

1,1

Comments

Also numbers k such that (47*10^k + 43)/9 is prime.

a(22) > 10^5. - Robert Price, Jul 10 2015

Links

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

Makoto Kamada, Prime numbers of the form 522...227.

Index entries for primes involving repunits.

Formula

a(n) = A101575(n) + 1.

Mathematica

Do[ If[ PrimeQ[(46*10^n + 43)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101575.

Sequence in context: A235267 A284379 A372718 * A225866 A332704 A378676

Adjacent sequences: A103007 A103008 A103009 * A103011 A103012 A103013

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

a(17)-a(18) from Kamada data by Robert Price, Dec 14 2010

a(19)-a(21) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

Status

approved