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%I #10 Jun 13 2022 02:26:06
%S 25,51,91,107,145,651,1473,2145,5577,12457
%N Numbers k such that 10^k - 9^(k+1) is prime.
%C a(11) > 10^5.
%e 25 is a term since 10^25 - 9^26 = 3538918110773326701067759, which is a prime number.
%t Select[Range[21, 100000], PrimeQ[10^# - 9^(# + 1)] &]
%o (PARI) is(n)=ispseudoprime(10^n-9^(n+1)) \\ _Charles R Greathouse IV_, Jun 08 2016
%Y Cf. A093713, A082103, A093717, A093793, A096185, A093794, A093795, A096186, A271883.
%K nonn,more
%O 1,1
%A _Robert Price_, Jun 01 2016
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