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A293592 Numbers k such that 3*10^k - 59 is prime. 0
2, 5, 7, 55, 70, 188, 248, 273, 385, 416, 479, 530, 574, 892, 1833, 4057, 4299, 6188, 14699, 21121, 88293, 89608, 95776, 162620, 196881 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
For k > 1, numbers k such that the digit 2 followed by k-2 occurrences of the digit 9 followed by the digits 41 is prime (see Example section).
a(26) > 2*10^5.
LINKS
Makoto Kamada, Search for 29w41.
EXAMPLE
2 is in this sequence because (3*10^2 - 59)/3 = 241 is prime.
Initial terms and associated primes:
a(1) = 2, 241;
a(2) = 5, 299941;
a(3) = 7, 29999941;
a(4) = 55, 29999999999999999999999999999999999999999999999999999941; etc.
MATHEMATICA
Select[Range[2, 100000], PrimeQ[(3*10^# - 59)/3] &]
CROSSREFS
Sequence in context: A182785 A358381 A041125 * A042257 A343833 A103056
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Oct 12 2017
EXTENSIONS
a(24)-a(25) from Robert Price, Sep 08 2018
STATUS
approved

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Last modified June 19 18:58 EDT 2024. Contains 373507 sequences. (Running on oeis4.)