A103094 Numbers n such that 9*10^n + 2*R_n + 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

5, 29, 60, 147, 186, 456, 678, 1373, 3378, 15726, 68231

Offset

1,1

Comments

Also numbers n such that (83*10^n+7)/9 is prime.

a(12) > 10^5. - Robert Price, Oct 31 2015

Links

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

Makoto Kamada, Prime numbers of the form 922...223.

Index entries for primes involving repunits.

Formula

a(n) = A101002(n) + 1.

Mathematica

Do[ If[ PrimeQ[(83*10^n + 7)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101002.

Sequence in context: A177831 A115706 A031394 * A341083 A341085 A301858

Adjacent sequences: A103091 A103092 A103093 * A103095 A103096 A103097

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(10) from Kamada data by Robert Price, Dec 14 2010

a(11) from Robert Price, Oct 31 2015

Status

approved