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A274676
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Numbers k such that 7*10^k + 13 is prime.
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4
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1, 3, 9, 12, 18, 19, 36, 37, 49, 67, 337, 893, 1924, 8044, 11610, 13560, 18777, 35376, 53601, 56022, 66488, 89801, 190210
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OFFSET
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1,2
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COMMENTS
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LINKS
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EXAMPLE
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3 is in this sequence because 7*10^3 + 13 = 7013 is prime.
4 is not in the sequence because 7*10^4 + 13 = 70013 = 53 * 1321.
Initial terms and associated primes:
a(1) = 1: 83;
a(2) = 3: 7013;
a(3) = 9: 7000000013;
a(4) = 12: 7000000000013, etc.
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MAPLE
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select(t -> isprime(7*10^t+13), [$1..2000]); # Robert Israel, Jul 03 2016
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MATHEMATICA
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Select[Range[0, 3000], PrimeQ[7 * 10^# + 13] &]
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PROG
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(Magma) [n: n in [1..800] | IsPrime(7*10^n+13)];
(PARI) is(n) = ispseudoprime(7*10^n+13) \\ Felix Fröhlich, Jul 03 2016
(PARI) lista(nn) = for(n=1, nn, if(ispseudoprime(7*10^n+13), print1(n, ", "))); \\ Altug Alkan, Jul 03 2016
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CROSSREFS
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Cf. numbers k such that 7*10^k + m is prime: A056804 (m=1), A097970 (m=3), A097954 (m=9), this sequence (m=13), A274677 (m=19), A274678 (m=27), A111021 (m=31), A274679 (m=33), A274700 (m=37), A274692 (m=43), A270974 (m=57).
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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a(18)-a(23) from Kamada data by Tyler Busby, Apr 15 2024
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STATUS
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approved
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