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 A283684 Numbers k such that 3*10^k + 17 is prime. 0

%I

%S 1,2,5,6,13,17,24,29,38,43,59,92,350,365,679,1016,2958,4434,6306,8819,

%T 11687,13484,22189,43034,69354,78146,78631,150182

%N Numbers k such that 3*10^k + 17 is prime.

%C For k>1, numbers such that the digit 3 followed by k-2 occurrences of the digit 0 followed by the digits 17 is prime (see Example section).

%C a(29) > 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 30w17.</a>

%e 2 is in this sequence because 3*10^2 + 17 = 317 is prime.

%e Initial terms and primes associated:

%e a(1) = 1, 47;

%e a(2) = 2, 317;

%e a(3) = 5, 300017;

%e a(4) = 6, 3000017;

%e a(5) = 13, 30000000000017; etc.

%t Select[Range[0, 100000], PrimeQ[3*10^# + 17] &]

%o (PARI) isok(n) = isprime((3*10^n + 17)); \\ _Indranil Ghosh_, Mar 14 2017

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

%K nonn,more,hard

%O 1,2

%A _Robert Price_, Mar 14 2017

%E a(28) from _Robert Price_, Jul 27 2018

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Last modified June 4 04:39 EDT 2020. Contains 334815 sequences. (Running on oeis4.)