A103072 Numbers n such that 8*10^n + R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

3, 9, 17, 153, 194, 641, 675, 1461, 26429, 48461, 72735

Offset

1,1

Comments

Also numbers n such that (73*10^n+53)/9 is prime.

a(12) > 10^5. - Robert Price, Oct 09 2015

Links

Table of n, a(n) for n=1..11.

Makoto Kamada, Prime numbers of the form 811...117.

Index entries for primes involving repunits.

Formula

a(n) = A101059(n) + 1.

Mathematica

Do[ If[ PrimeQ[(73*10^n + 53)/9], Print[n]], {n, 0, 10000}]

Prog

(PARI) for(n=1, 1e6, if(isprime((73*10^n+53)/9), print1(n", "))) \\ Altug Alkan, Oct 09 2015

Crossrefs

Cf. A002275, A101059.

Sequence in context: A056404 A056405 A009216 * A109228 A376636 A355636

Adjacent sequences: A103069 A103070 A103071 * A103073 A103074 A103075

Keyword

nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(9) from Kamada data by Robert Price, Dec 14 2010

a(10) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

a(11) from Robert Price, Oct 09 2015

Status

approved