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A272621
Numbers n such that 10^n-9^(n-1) is prime.
0
3, 9, 15, 155, 217, 281, 287, 491, 563, 581, 983, 2243, 4375, 8409, 98669
OFFSET
1,1
COMMENTS
a(16) > 10^5.
EXAMPLE
3 is a member since 10^3-9^2 = 1000-81 = 919 which is a prime number.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[10^# - 9^(# - 1)] &]
PROG
(PARI) is(n)=ispseudoprime(10^n-9^(n-1)) \\ Charles R Greathouse IV, Jun 13 2017
KEYWORD
nonn,more
AUTHOR
Robert Price, May 03 2016
STATUS
approved