A103024 Numbers n such that 5*10^n + 8*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 4, 8, 13, 16, 44, 439, 608, 1201, 2725, 5210, 59389, 118216, 198529

Offset

1,2

Comments

Also numbers n such that (53*10^n+1)/9 is prime.

Links

Table of n, a(n) for n=1..14.

Makoto Kamada, Prime numbers of the form 588...889.

Index entries for primes involving repunits.

Formula

a(n) = A101589(n) + 1.

Mathematica

Do[ If[ PrimeQ[(53*10^n + 1)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101589.

Sequence in context: A311755 A311756 A311757 * A131041 A311758 A311759

Adjacent sequences: A103021 A103022 A103023 * A103025 A103026 A103027

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

Addition of a(12)-a(14) from Kamada data by Robert Price, Dec 12 2010

Status

approved