A103087 Numbers n such that 8*10^n + 6*R_n - 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 1, 2, 3, 13, 19, 62, 80, 126, 168, 195, 309, 410, 481, 608, 741, 879, 1176, 2688, 6236, 16294, 17317, 31574, 34861, 35392, 48726

Offset

1,3

Comments

Also numbers n such that (26*10^n-11)/3 is prime.

a(27) > 10^5. - Robert Price, Oct 25 2015

Links

Table of n, a(n) for n=1..26.

Makoto Kamada, Prime numbers of the form 866...663.

Index entries for primes involving repunits.

Formula

a(n) = A101074(n-1) + 1, for n>1.

Mathematica

Do[ If[ PrimeQ[(26*10^n - 11)/3], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101074.

Sequence in context: A080359 A193507 A368396 * A302485 A135118 A274905

Adjacent sequences: A103084 A103085 A103086 * A103088 A103089 A103090

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(21)-a(22) from Kamada data by Robert Price, Dec 14 2010

a(23)-a(26) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

Inserted a(1)=0 by Robert Price, Oct 25 2015

Status

approved