A103033 Numbers n such that 6*10^n + 3*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 3, 4, 5, 6, 10, 13, 58, 96, 178, 360, 420, 455, 1008, 1517, 2975, 3999, 5425, 10819, 16036, 32076, 47237, 111385, 190935

Offset

1,2

Comments

Also numbers n such that (19*10^n+11)/3 is prime.

a(25) > 3*10^5. - Robert Price, Oct 26 2023

Links

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

Makoto Kamada, Prime numbers of the form 633...337.

Index entries for primes involving repunits.

Formula

a(n) = A101526(n) + 1.

Mathematica

Do[ If[ PrimeQ[(19*10^n + 11)/3], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101526.

Sequence in context: A174057 A335231 A164977 * A099561 A110300 A143713

Adjacent sequences: A103030 A103031 A103032 * A103034 A103035 A103036

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

Addition of a(19)-a(20) from Kamada data by Robert Price, Dec 10 2010

a(21)-a(22) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

a(23)-a(24) from Robert Price, Oct 26 2023

Status

approved