|
%I #14 May 26 2024 14:59:22
%S 1,2,4,5,7,10,16,19,28,37,41,44,53,311,490,1252,4360,4732,5575,6833,
%T 8878,11171,11396,13079,14903,76615
%N Numbers k such that (76*10^k + 167)/9 is prime.
%C For k > 1, numbers k such that the digit 8 followed by k-2 occurrences of the digit 4 followed by the digits 63 is prime (see Example section).
%C a(27) > 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/prime_difficulty.txt">Search for 84w63</a>.
%e 4 is in this sequence because (76*10^4+167)/9 = 84463 is prime.
%e Initial terms and associated primes:
%e a(1) = 1, 103;
%e a(2) = 2, 863;
%e a(3) = 4, 84463;
%e a(4) = 5, 844463;
%e a(5) = 7, 84444463, etc.
%t Select[Range[0, 100000], PrimeQ[(76*10^#+167)/9] &]
%o (PARI) is(n)=ispseudoprime((76*10^n+167)/9) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
%K nonn,more
%O 1,2
%A _Robert Price_, Aug 09 2016
|
