A102959 Numbers n such that 2*10^n + 7*R_n + 2 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 4, 34, 36, 42, 52, 163, 208, 216, 1417, 14646, 22794, 25648, 32515, 51421

Offset

1,2

Comments

Also numbers n such that (25*10^n+11)/9 is prime.

a(16) > 10^5. - Robert Price, Mar 12 2015

Links

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

Makoto Kamada, Prime numbers of the form 277...779.

Index entries for primes involving repunits.

Formula

a(n) = A101968(n) + 1.

Mathematica

Do[ If[ PrimeQ[(25*10^n + 11)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101968.

Sequence in context: A113086 A058153 A020197 * A057959 A220168 A227397

Adjacent sequences: A102956 A102957 A102958 * A102960 A102961 A102962

Keyword

more,nonn

Author

Robert G. Wilson v, Dec 17 2004

Extensions

a(11)-a(13) from Kamada data by Robert Price, Dec 14 2010

a(14) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

a(15) from Robert Price, Mar 12 2015

Status

approved