cp's OEIS Frontend

A277066 Numbers k such that (266*10^k - 11) / 3 is prime.

%I A277066 #20 Jun 09 2024 18:06:32
%S A277066 1,2,3,4,7,9,10,14,28,58,93,121,135,207,350,423,602,859,1026,1864,
%T A277066 1966,13738,23299,28126,38691,39403,47499,93577,124022,177577
%N A277066 Numbers k such that (266*10^k - 11) / 3 is prime.
%C A277066 For k > 0, numbers k such that the digits 88 followed by k-1 occurrences of the digit 6 followed by the digit 3 is prime (see Example section).
%C A277066 a(31) > 3*10^5.
%H A277066 Makoto Kamada, <a href="https://stdkmd.net/nrr">Factorization of near-repdigit-related numbers</a>.
%H A277066 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 886w3</a>.
%e A277066 3 is in this sequence because (266*10^3 - 11) / 3 = 88663 is prime.
%e A277066 Initial terms and associated primes:
%e A277066 a(1) = 1, 883;
%e A277066 a(2) = 2, 8863;
%e A277066 a(3) = 3, 88663;
%e A277066 a(4) = 4, 886663;
%e A277066 a(5) = 7, 886666663, etc.
%t A277066 Select[Range[0, 100000], PrimeQ[(266*10^# - 11) / 3] &]
%o A277066 (PARI) is(n)=ispseudoprime((266*10^n - 11)/3) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y A277066 Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A271269.
%K A277066 nonn,more
%O A277066 1,2
%A A277066 _Robert Price_, Sep 27 2016
%E A277066 a(29)-a(30) from _Robert Price_, Apr 01 2020