A103036 Numbers n such that 6*10^n + 4*R_n + 3 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 2, 5, 10, 40, 47, 58, 73, 92, 113, 124, 130, 887, 1234, 1538, 2063, 2591, 2786, 3145, 21688, 32381, 39170, 47791, 83878

Offset

1,2

Comments

Also numbers n such that (58*10^n+23)/9 is prime.

a(25) > 10^5. - Robert Price, Sep 15 2015

Links

Table of n, a(n) for n=1..24.

Makoto Kamada, Prime numbers of the form 644...447.

Index entries for primes involving repunits.

Formula

a(n) = A101529(n) + 1.

Mathematica

Do[ If[ PrimeQ[(58*10^n + 23)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101529.

Sequence in context: A155217 A004143 A266162 * A018439 A349449 A018451

Adjacent sequences: A103033 A103034 A103035 * A103037 A103038 A103039

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

a(20) from Kamada data by Robert Price, Dec 14 2010

a(21)-a(23) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

a(24) from Robert Price, Sep 15 2015

Status

approved