A102951 Numbers k such that 2*10^k + 3*R_k + 6 is prime, where R_k = 11...1 is the repunit (A002275) of length k.

1, 2, 3, 4, 8, 11, 13, 24, 28, 52, 54, 94, 297, 657, 1006, 5347, 8189, 9314, 23055, 53287, 64807, 218644

Offset

1,2

Comments

Also numbers k such that (7*10^k + 17)/3 is prime.

a(23) > 3*10^5. - Robert Price, Jul 13 2023

Links

Table of n, a(n) for n=1..22.

Makoto Kamada, Prime numbers of the form 233...339.

Index entries for primes involving repunits.

Formula

a(n) = A101956(n) + 1. - Robert Price, Nov 25 2014

Mathematica

Do[ If[ PrimeQ[(7*10^n + 17)/3], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101956.

Sequence in context: A279194 A050727 A295323 * A015935 A135909 A046812

Adjacent sequences: A102948 A102949 A102950 * A102952 A102953 A102954

Keyword

more,nonn

Author

Robert G. Wilson v, Dec 17 2004

Extensions

Addition of a(19) from Kamada data by Robert Price, Dec 10 2010

a(20)-a(21) from Kamada data by Robert Price, Nov 25 2014

a(22) from Robert Price, Jul 13 2023

Status

approved