A102979 Numbers n such that 3*10^n + 8*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 1, 6, 10176, 56898

Offset

1,3

Comments

Also numbers n such that (35*10^n-17)/9 is prime.

a(6) > 10^5. - Robert Price, Mar 30 2015

Links

Table of n, a(n) for n=1..5.

Makoto Kamada, Prime numbers of the form 388...887.

Index entries for primes involving repunits.

Formula

a(n) = A101846(n-1) + 1.

Mathematica

Do[ If[ PrimeQ[(35*10^n - 17)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101846.

Sequence in context: A361901 A329911 A088021 * A069942 A261823 A146202

Adjacent sequences: A102976 A102977 A102978 * A102980 A102981 A102982

Keyword

more,nonn

Author

Robert G. Wilson v, Dec 17 2004

Extensions

Additional term 10176 (a PRP) from Serge Batalov, Oct 12 2008

Addition of a(5) from Kamada data by Robert Price, Dec 13 2010

Status

approved