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A281142 Numbers k such that (25*10^k - 13)/3 is prime. 0
1, 2, 3, 6, 8, 18, 21, 33, 56, 301, 381, 426, 769, 1123, 1638, 2037, 2660, 3284, 4723, 5686, 17227, 22084, 25009, 36176, 125076, 141019 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
For k>1, numbers such that the digit 8 followed by k-2 occurrences of the digit 3 followed by the digits 29 is prime (see Example section).
a(27) > 2*10^5.
LINKS
Makoto Kamada, Search for 83w29.
EXAMPLE
3 is in this sequence because (25*10^3 - 13) / 3 = 8329 is prime.
Initial terms and primes associated:
a(1) = 1, 79;
a(2) = 2, 829;
a(3) = 3, 8329;
a(4) = 6, 8333329;
a(5) = 8, 833333329; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(25*10^# - 13) / 3] &]
CROSSREFS
Sequence in context: A368687 A330442 A103065 * A110448 A005508 A022542
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Jan 15 2017
EXTENSIONS
a(25)-a(26) from Robert Price, Sep 23 2019
STATUS
approved

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Last modified March 28 15:28 EDT 2024. Contains 371254 sequences. (Running on oeis4.)