A110285 Numbers k such that k*10^k + k - 1 is prime.

168, 760, 2154, 9172

Offset

1,1

Comments

Not proved, only Fermat and Lucas PRPs. Next term is greater than 12000. Concerning primes of the form k * 10^k + k + 1, only k = 42 yields one for all k up to 7700.

Next term is greater than 72000. - Michael S. Branicky, Dec 24 2024

Links

Table of n, a(n) for n=1..4.

Prog

(PARI) is(n)=ispseudoprime(n*10^n+n-1) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Sequence in context: A234816 A245868 A251461 * A302887 A235071 A235064

Adjacent sequences: A110282 A110283 A110284 * A110286 A110287 A110288

Keyword

more,nonn,changed

Author

Jason Earls, Sep 07 2005

Status

approved