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A283236 Numbers k such that (86*10^k - 329)/9 is prime. 0
1, 2, 7, 22, 50, 76, 77, 130, 193, 259, 347, 590, 665, 838, 1516, 3512, 3566, 3688, 5393, 5408, 5875, 10160, 24238, 127967 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 9 followed by k-2 occurrences of the digit 5 followed by the digits 19 is prime (see Example section).
a(25) > 2*10^5.
LINKS
Makoto Kamada, Search for 95w19.
EXAMPLE
2 is in this sequence because (86*10^2 - 329)/9 = 919 is prime.
Initial terms and associated primes:
a(1) = 1, 59;
a(2) = 2, 919;
a(3) = 7, 95555519;
a(4) = 22, 95555555555555555555519;
a(5) = 50, 955555555555555555555555555555555555555555555555519; etc.
MATHEMATICA
Select[Range[1, 100000], PrimeQ[(86*10^# - 329)/9] &]
CROSSREFS
Sequence in context: A284921 A174236 A131856 * A007344 A153536 A153564
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Mar 03 2017
EXTENSIONS
a(24) from Robert Price, Jan 11 2020
STATUS
approved

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Last modified July 15 21:59 EDT 2024. Contains 374334 sequences. (Running on oeis4.)