A103041 Numbers n such that 6*10^n + 5*R_n + 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

2, 5, 8, 17, 20, 65, 83, 90, 108, 252, 335, 1488, 6356, 65712, 96798

Offset

1,1

Comments

Also numbers n such that (59*10^n+31)/9 is prime.

a(16) > 10^5. - Robert Price, Sep 13 2015

Links

Table of n, a(n) for n=1..15.

Makoto Kamada, Prime numbers of the form 655...559.

Index entries for primes involving repunits.

Formula

a(n) = A101534(n) + 1.

Mathematica

Do[ If[ PrimeQ[(59*10^n + 31)/9], Print[n]], {n, 0, 10000}]

Prog

(PARI) is(n)=isprime(6*10^n + 5*(10^n-1)/9 + 4) \\ Anders Hellström, Sep 13 2015

Crossrefs

Cf. A002275, A101534.

Sequence in context: A055236 A345430 A214124 * A216307 A176223 A006827

Adjacent sequences: A103038 A103039 A103040 * A103042 A103043 A103044

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

a(14)-a(15) from Robert Price, Sep 13 2015

Status

approved