A103038 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.

0, 1, 3, 4, 10, 22, 40, 54, 81, 84, 106, 193, 597, 681, 1363, 1876, 4024, 14163, 18733, 20842, 23728, 26419, 31450, 44694, 64767

Offset

1,3

Comments

Also numbers n such that (59*10^n-41)/9 is prime.

a(26) > 10^5. - Robert Price, Sep 11 2015

Links

Table of n, a(n) for n=1..25.

Makoto Kamada, Prime numbers of the form 655...551.

Index entries for primes involving repunits.

Formula

a(n) = A101531(n-1) + 1 for n>1.

Mathematica

Do[ If[ PrimeQ[(59*10^n - 41)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101531.

Sequence in context: A109887 A200981 A266729 * A143108 A169790 A014009

Adjacent sequences: A103035 A103036 A103037 * A103039 A103040 A103041

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 18 2005

Extensions

a(18)-a(22) from Kamada data by Robert Price, Dec 14 2010

a(23)-a(24) from Erik Branger May 01 2013 by Ray Chandler, Aug 16 2013

Inserted a(1)=0 by Robert Price, Sep 11 2015

a(25) from Robert Price, Sep 11 2015

Status

approved