A103101 Numbers n such that 9*10^n + 5*R_n - 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 2, 20, 104, 329, 1442, 1721, 24887

Offset

1,2

Comments

Also numbers n such that (86*10^n-23)/9 is prime.

a(9) > 10^5. - Robert Price, Nov 08 2015

Links

Table of n, a(n) for n=1..8.

Makoto Kamada, Prime numbers of the form 955...553.

Index entries for primes involving repunits.

Formula

a(n) = A101010(n-1) + 1, for n>1.

Mathematica

Do[ If[ PrimeQ[(86*10^n - 23)/9], Print[n]], {n, 0, 10000}]

Prog

(PARI) for(n=0, 1e5, if(isprime((86*10^n-23)/9), print1(n, ", "))); \\ Altug Alkan, Nov 08 2015

Crossrefs

Cf. A002275, A101010.

Sequence in context: A220856 A035599 A222556 * A267678 A009357 A052361

Adjacent sequences: A103098 A103099 A103100 * A103102 A103103 A103104

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(8) from Kamada data by Robert Price, Dec 14 2010

Inserted a(1)=0 by Robert Price, Nov 08 2015

Status

approved