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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified August 5 20:11 EDT 2021. Contains 346488 sequences. (Running on oeis4.)