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 A290432 Numbers k such that 9*10^k + 59 is prime. 0

%I

%S 1,3,4,6,7,12,17,28,46,75,105,309,351,460,774,785,2206,5739,12427,

%T 14501,17950,68331,106559,166996

%N Numbers k such that 9*10^k + 59 is prime.

%C For k > 1, numbers such that the digit 9 followed by k-2 occurrences of the digit 0 followed by the digits 59 is prime (see Example section).

%C a(25) > 2*10^5.

%H Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>.

%H Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/primedifficulty.txt">Search for 90w59</a>,

%e 3 is in this sequence because 9*10^3 + 59 = 9059 is prime.

%e Initial terms and primes associated:

%e a(1) = 1, 149;

%e a(2) = 3, 9059;

%e a(3) = 4, 90059;

%e a(4) = 6, 9000059;

%e a(5) = 7, 90000059; etc.

%t Select[Range[0, 100000], PrimeQ[9*10^# + 59] &]

%Y Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.

%K nonn,more,hard

%O 1,2

%A _Robert Price_, Oct 06 2017

%E a(23)-a(24) from _Robert Price_, Jan 13 2020

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Last modified April 1 05:29 EDT 2020. Contains 333155 sequences. (Running on oeis4.)