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A295668
Numbers k such that (14*10^k + 79)/3 is prime.
0
0, 1, 6, 7, 8, 10, 19, 22, 42, 48, 100, 190, 298, 535, 768, 1003, 1904, 7512, 26725, 27517, 33676, 74540
OFFSET
1,3
COMMENTS
For k > 1, numbers k such that the digit 4 followed by k-2 occurrences of the digit 6 followed by the digits 93 is prime (see Example section).
a(23) > 2*10^5.
EXAMPLE
1 is in this sequence because (14*10^1 + 79)/3 = 73 is prime.
Initial terms and associated primes:
a(1) = 0, 31;
a(2) = 1, 73;
a(3) = 6, 4666693;
a(4) = 7, 46666693;
a(5) = 8, 466666693; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(14*10^# + 79)/3] &] (* fixed by Shawn A. Broyles, Nov 27 2017 *)
PROG
(PARI) is(k) = ispseudoprime((14*10^k + 79)/3) \\ Iain Fox, Nov 27 2017
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Nov 25 2017
STATUS
approved