OFFSET
1,2
COMMENTS
a(1) through a(17) have been proved to be prime with WinPFGW or pfgw.
a(18) > 20000. - Giovanni Resta, Feb 19 2013
a(18) > 100000. - James G. Merickel Jun 02 2014
EXAMPLE
a(3) = 3 because 100^3 + 10^3 - 1 = 1000999, a prime.
MATHEMATICA
Select[Range[700], PrimeQ[100^# + 10^# - 1] & ] (* Giovanni Resta, Feb 19 2013 *)
PROG
(PARI) is(n)=ispseudoprime(100^n+10^n-1) \\ Charles R Greathouse IV, Feb 20 2017
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Jason Earls, Aug 13 2004
EXTENSIONS
a(17) from Giovanni Resta, Feb 19 2013
STATUS
approved