A103090 Numbers n such that 8*10^n + 7*R_n - 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 7, 36, 99, 325, 1227, 9261, 9414, 11115, 25149, 43212

Offset

1,2

Comments

Also numbers n such that (79*10^n-43)/9 is prime.

Links

Table of n, a(n) for n=1..11.

Makoto Kamada, Prime numbers of the form 877...773.

Index entries for primes involving repunits.

Formula

a(n) = A101077(n) + 1.

Mathematica

Do[ If[ PrimeQ[(79*10^n - 43)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101077.

Sequence in context: A018199 A063168 A163683 * A250414 A212141 A212088

Adjacent sequences: A103087 A103088 A103089 * A103091 A103092 A103093

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(9)-a(11) from Kamada data by Robert Price, Dec 14 2010

Status

approved