A103042 Numbers n such that 6*10^n + 7*R_n - 4 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

0, 2, 156, 1055, 1997, 8930, 9563, 19560, 26838, 63857

Offset

1,2

Comments

Also numbers n such that (61*10^n-43)/9 is prime.

a(11) > 10^5. - Robert Price, Sep 12 2015

Links

Table of n, a(n) for n=1..10.

Makoto Kamada, Prime numbers of the form 677...773.

Index entries for primes involving repunits.

Formula

a(n) = A101535(n-1) + 1 for n>1.

Mathematica

Do[ If[ PrimeQ[(61*10^n - 43)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101535.

Sequence in context: A332585 A000725 A151614 * A284458 A260886 A142006

Adjacent sequences: A103039 A103040 A103041 * A103043 A103044 A103045

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

a(8)-a(9) from Kamada data by Robert Price, Dec 14 2010

Inserted a(1)=0 by Robert Price, Sep 12 2015

a(10) from Robert Price, Sep 12 2015

Status

approved