A102990 Numbers n such that 4*10^n + 3*R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

2, 3, 6, 11, 15, 26, 28, 51, 150, 182, 228, 407, 638, 3581, 4125, 4983, 5666, 15890, 27743, 43362, 55367, 60744, 73701

Offset

1,1

Comments

Also numbers n such that (13*10^n+17)/3 is prime.

a(24) > 10^5. - Robert Price, Jun 25 2015

Links

Table of n, a(n) for n=1..23.

Makoto Kamada, Prime numbers of the form 433...339.

Index entries for primes involving repunits.

Formula

a(n) = A101725(n) + 1.

Mathematica

Do[ If[ PrimeQ[(13*10^n + 17)/3], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101725.

Sequence in context: A005211 A298702 A076307 * A351203 A138519 A138520

Adjacent sequences: A102987 A102988 A102989 * A102991 A102992 A102993

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 17 2005

Extensions

Addition of a(18)-a(19) from Kamada data by Robert Price, Dec 10 2010

a(20) from Erik Branger, May 01 2013, submitted by Ray Chandler, Aug 16 2013

a(21)-a(23) from Robert Price, Jun 25 2015

Status

approved