A102936 Numbers k such that 10^k + 5*R_k - 2 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

1, 3, 6, 15, 70, 76, 13024, 60346

Offset

1,2

Comments

Also numbers k such that (14*10^k - 23)/9 is prime.

a(9) > 10^5. - Robert Price, Apr 10 2015

Links

Table of n, a(n) for n=1..8.

Makoto Kamada, Prime numbers of the form 155...553.

Index entries for primes involving repunits.

Formula

a(n) = A102019(n) + 1.

Mathematica

Do[ If[ PrimeQ[(14*10^n - 23)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A102019.

Sequence in context: A241269 A102356 A208662 * A009192 A013273 A013277

Adjacent sequences: A102933 A102934 A102935 * A102937 A102938 A102939

Keyword

more,nonn

Author

Robert G. Wilson v, Dec 16 2004

Extensions

Addition of a(7) from Kamada data by Robert Price, Dec 13 2010

a(8) from Robert Price, Apr 10 2015

Status

approved