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A274679 Numbers k such that 7*10^k + 33 is prime.

%I A274679 #22 Jun 02 2024 14:03:16
%S A274679 1,2,6,10,17,29,53,107,133,596,852,1068,1186,1356,1673,1987,3170,3312,
%T A274679 5819,6655,19267,20009,29302,72614,170348,178566
%N A274679 Numbers k such that 7*10^k + 33 is prime.
%H A274679 Makoto Kamada, <a href="https://stdkmd.net/nrr/prime/prime_difficulty.txt">Search for 70w33</a>.
%e A274679 2 is in this sequence because 7*10^2 + 33 = 733 is prime.
%e A274679 4 is not in the sequence because 7*10^4 + 33 = 70033 = 59 * 1187.
%e A274679 Initial terms and associated primes:
%e A274679 a(1) = 1: 103;
%e A274679 a(2) = 2: 733;
%e A274679 a(3) = 6: 7000033;
%e A274679 a(4) = 10: 70000000033, etc.
%t A274679 Select[Range[0, 3000], PrimeQ[7 10^# + 33] &]
%o A274679 (Magma) [n: n in [1..500] | IsPrime(7*10^n+33)];
%o A274679 (PARI) lista(nn) = for(n=1, nn, if(ispseudoprime(7*10^n+33), print1(n, ", "))); \\ _Altug Alkan_, Jul 05 2016
%Y A274679 Cf. similar sequences listed in A274676.
%K A274679 nonn,more
%O A274679 1,2
%A A274679 _Vincenzo Librandi_, Jul 04 2016
%E A274679 a(19)-a(20) from _Michael S. Branicky_, Aug 16 2021
%E A274679 a(21)-a(26) from Kamada data by _Tyler Busby_, Apr 14 2024