A103093 Numbers n such that 9*10^n + 2*R_n - 1 is prime, where R_n = 11...1 is the repunit (A002275) of length n.

3, 4, 24, 39, 63, 76, 108, 166, 520, 1810, 2349, 2562, 5784, 6448, 11692, 16036, 17554

Offset

1,1

Comments

Also numbers n such that (83*10^n-11)/9 is prime.

a(18) > 10^5. - Robert Price, Nov 03 2015

Links

Table of n, a(n) for n=1..17.

Makoto Kamada, Prime numbers of the form 922...221.

Index entries for primes involving repunits.

Formula

a(n) = A101001(n) + 1.

Mathematica

Do[ If[ PrimeQ[(83*10^n - 11)/9], Print[n]], {n, 0, 10000}]

Crossrefs

Cf. A002275, A101001.

Sequence in context: A047180 A051394 A050801 * A124632 A048091 A189738

Adjacent sequences: A103090 A103091 A103092 * A103094 A103095 A103096

Keyword

more,nonn

Author

Robert G. Wilson v, Jan 19 2005

Extensions

a(15)-a(17) from Kamada data by Robert Price, Dec 14 2010

Status

approved