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A096594
Numbers n such that 100^n + 10^n - 1 is prime.
5
1, 2, 3, 5, 6, 7, 9, 13, 26, 42, 153, 188, 204, 282, 699, 2886, 11597
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
Sequence in context: A292938 A056900 A226808 * A100693 A030159 A030161
KEYWORD
more,nonn
AUTHOR
Jason Earls, Aug 13 2004
EXTENSIONS
a(17) from Giovanni Resta, Feb 19 2013
STATUS
approved