A102992 Numbers n such that 4*10^n + 5*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 2, 4, 5, 13, 22, 25, 28, 38, 67, 142, 284, 295, 380, 397, 1217, 1640, 2885, 3286, 7735, 29306

Offset

1,2

Comments

Also numbers n such that (41*10^n+13)/9 is prime.

a(22) > 10^5. - Robert Price, May 22 2015

Links

Table of n, a(n) for n=1..21.

Makoto Kamada, Prime numbers of the form 455...557.

Index entries for primes involving repunits.

Formula

a(n) = A101727(n) + 1.

Mathematica

Do[ If[ PrimeQ[(41*10^n + 13)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101727.

Sequence in context: A079407 A078652 A289491 * A273097 A232207 A136563

Adjacent sequences: A102989 A102990 A102991 * A102993 A102994 A102995

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 17 2005

Extensions

Addition of a(21) from Kamada data by Robert Price, Dec 09 2010

Status

approved