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A280584 Numbers k such that (14*10^k - 83)/3 is prime. 0
1, 2, 3, 4, 6, 10, 11, 24, 53, 83, 97, 156, 157, 162, 182, 233, 355, 499, 629, 1252, 6378, 8366, 26406, 35345, 107694, 126784, 195234, 255805 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
For k>1, numbers such that the digit 4 followed by k-2 occurrences of the digit 6 followed by the digits 39 is prime (see Example section).
a(29) > 3*10^5.
LINKS
Makoto Kamada, Search for 46w39.
EXAMPLE
4 is in this sequence because (14*10^4 - 83) / 3 = 46639 is prime.
Initial terms and primes associated:
a(1) = 1, 19;
a(2) = 2, 439;
a(3) = 3, 4639;
a(4) = 4, 46639;
a(5) = 6, 4666639; etc.
MATHEMATICA
Select[Range[1, 100000], PrimeQ[(14*10^# - 83) / 3] &]
PROG
(PARI) is(n)=ispseudoprime((14*10^n - 83)/3) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Sequence in context: A005453 A180242 A187966 * A225649 A225651 A191149
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Jan 05 2017
EXTENSIONS
a(25)-a(27) from Robert Price, Dec 23 2018
a(28) from Robert Price, Jun 17 2023
STATUS
approved

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Last modified March 28 14:38 EDT 2024. Contains 371254 sequences. (Running on oeis4.)