

A274677


Numbers n such that 7*10^n + 19 is prime.


1



1, 2, 3, 4, 27, 32, 63, 69, 107, 145, 154, 173, 190, 271, 412, 1219, 1509, 2392, 4444
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OFFSET

1,2


COMMENTS

No term is divisible by 6 (A047253) because 7*1000000^n + 19 = 7*(76923*13 + 1)^n + 19 is divisible by 13 and is therefore not prime.  Bruno Berselli, Jul 05 2016


LINKS

Table of n, a(n) for n=1..19.


EXAMPLE

3 is in this sequence because 7*10^3 + 19 = 7019 is prime.
5 is not in the sequence because 7*10^5 + 19 = 79*8861.
Initial terms and associated primes:
a(1) = 1: 89;
a(2) = 2: 719;
a(3) = 3: 7019;
a(4) = 4: 70019, etc.


MATHEMATICA

Select[Range[0, 3000], PrimeQ[7 10^# + 19] &]


PROG

(MAGMA) [n: n in [1..800]  IsPrime(7*10^n+19)];
(PARI) lista(nn) = for(n=1, nn, if(ispseudoprime(7*10^n+19), print1(n, ", "))); \\ Altug Alkan, Jul 05 2016


CROSSREFS

Subsequence of A047253.
Cf. similar sequences listed in A274676.
Sequence in context: A293000 A141565 A098549 * A100604 A062931 A059614
Adjacent sequences: A274674 A274675 A274676 * A274678 A274679 A274680


KEYWORD

nonn,more


AUTHOR

Vincenzo Librandi, Jul 04 2016


STATUS

approved



