A103108 Numbers n such that 9*10^n + 8*R_n - 5 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

2, 3, 32, 42, 75, 368, 1392, 16350, 49101, 49689, 91839

Offset

1,1

Comments

Also numbers n such that (89*10^n-53)/9 is prime.

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

Links

Table of n, a(n) for n=1..11.

Makoto Kamada, Prime numbers of the form 988...883.

Index entries for primes involving repunits.

Formula

a(n) = A101017(n) + 1.

Mathematica

Do[ If[ PrimeQ[(89*10^n - 53)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101017.

Sequence in context: A176894 A041053 A212763 * A107124 A141049 A354612

Adjacent sequences: A103105 A103106 A103107 * A103109 A103110 A103111

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

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

a(9)-a(10) from Erik Branger May 01 2013 by Ray Chandler, Aug 17 2013

a(11) from Robert Price, Nov 12 2015

Status

approved