A103028 Numbers n such that 6*10^n + R_n + 6 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 2, 32, 43, 973, 1195, 4471, 5684, 7988, 46885

Offset

1,2

Comments

Also numbers n such that (55*10^n+53)/9 is prime.

a(11) > 10^5. - Robert Price, Sep 07 2015

Links

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

Makoto Kamada, Prime numbers of the form 611...117.

Index entries for primes involving repunits.

Formula

a(n) = A101520(n) + 1.

Mathematica

Do[ If[ PrimeQ[(55*10^n + 53)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101520.

Sequence in context: A306950 A193419 A160557 * A139732 A037313 A122127

Adjacent sequences: A103025 A103026 A103027 * A103029 A103030 A103031

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

a(10) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

Status

approved