OFFSET
1,2
COMMENTS
Numbers k such that 10^(k+1) + (10^k-1) is a prime.
LINKS
Gary Barnes, Primes of the form k*10^n-1
Makoto Kamada, Search for 109w.
MATHEMATICA
Do[ If[ PrimeQ[10^(n + 1) + (10^n - 1)], Print[n]], {n, 9500}]
PROG
(PARI) is(n)=ispseudoprime(11*10^n-1) \\ Charles R Greathouse IV, Jun 12 2017
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Nov 15 2005
EXTENSIONS
a(16)-a(19) from Ray Chandler, Sep 16 2013
a(20)-a(21) from P. Kurtovic submitted by Ray Chandler, Sep 17 2013
a(22)-a(24) from Kamada data by Tyler Busby, Apr 14 2024
STATUS
approved