A103059 Numbers n such that 7*10^n + 4*R_n + 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

1, 4, 7, 34, 82, 451, 772, 2554, 6250, 15137, 20074, 37378, 53068

Offset

1,2

Comments

Also numbers n such that (67*10^n+41)/9 is prime.

a(14) > 10^5. - Robert Price, Sep 27 2015

Links

Table of n, a(n) for n=1..13.

Makoto Kamada, Prime numbers of the form 744...449.

Index entries for primes involving repunits.

Formula

a(n) = A101142(n) + 1.

Mathematica

Do[ If[ PrimeQ[(67*10^n + 41)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101142.

Sequence in context: A237424 A143547 A149090 * A123809 A140981 A283819

Adjacent sequences: A103056 A103057 A103058 * A103060 A103061 A103062

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(10)-a(11) from Kamada data by Robert Price, Dec 14 2010

a(12) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

a(13) from Robert Price, Sep 27 2015

Status

approved