cp's OEIS Frontend

A271107 Numbers k such that 33*10^k + 1 is prime.

%I A271107 #15 May 02 2024 22:54:51
%S A271107 1,2,5,6,7,8,29,47,145,205,227,505,553,600,787,809,1305,1447,1593,
%T A271107 2285,4763,5679,9133,12516,14869,16536,33402,36085,51933,56443,69133
%N A271107 Numbers k such that 33*10^k + 1 is prime.
%C A271107 Numbers k such that the digits 33 followed by k-1 occurrences of the digit 0 followed by the digit 1 is prime (see Example section).
%C A271107 a(32) > 10^5.
%H A271107 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 330w1</a>.
%e A271107 5 is in this sequence because 33*10^5+1 = 3300001 is prime.
%e A271107 Initial terms and associated primes:
%e A271107 a(1) = 1, 331;
%e A271107 a(2) = 2, 3301;
%e A271107 a(3) = 5, 3300001;
%e A271107 a(4) = 6, 33000001;
%e A271107 a(5) = 7, 330000001;
%e A271107 a(6) = 8, 3300000001, etc.
%t A271107 Select[Range[0, 100000], PrimeQ[33*10^#+1] &]
%o A271107 (PARI) lista(nn) = for(n=1, nn, if(ispseudoprime(33*10^n+1), print1(n, ", "))); \\ _Altug Alkan_, Mar 31 2016
%Y A271107 Cf. A056654, A268448, A269303, A270339, A270613, A270831, A270890, A270929, A270974.
%K A271107 nonn,base,more
%O A271107 1,2
%A A271107 _Robert Price_, Mar 30 2016