A103088 Numbers k such that 8*10^k + 6*R_k + 3 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

0, 1, 3, 17, 19, 33, 39, 169, 453, 611, 883, 1473, 6511, 9647, 21593, 39991, 40157, 71503

Offset

1,3

Comments

Also numbers k such that (26*10^k+7)/3 is prime.

Links

Table of n, a(n) for n=1..18.

Makoto Kamada, Prime numbers of the form 866...669.

Index entries for primes involving repunits.

Formula

a(n) = A101075(n-1) + 1 for n >= 2.

Mathematica

Do[ If[ PrimeQ[(26*10^k + 7)/3], Print[k]], {k, 0, 10000}]

Crossrefs

Cf. A002275, A101075.

Sequence in context: A340408 A339544 A029473 * A226925 A259772 A082387

Adjacent sequences: A103085 A103086 A103087 * A103089 A103090 A103091

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(15)-a(17) from Kamada data by Robert Price, Dec 14 2010

a(1)=0 inserted by Georg Fischer, Jan 03 2021

a(18) from Kamada data by Tyler Busby, May 03 2024

Status

approved