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A293863 Numbers k such that (167*10^k - 17)/3 is prime. 0
3, 5, 13, 15, 21, 39, 45, 75, 171, 229, 293, 321, 355, 359, 1411, 2245, 3121, 8466, 9368, 40111, 102315, 126637, 173571 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
For k>1, numbers such that the digits 55 followed by k-2 occurrences of the digit 6 followed by the digit 1 is prime (see Example section).
a(24) > 2*10^5.
LINKS
Makoto Kamada, Search for 556w1.
EXAMPLE
3 is in this sequence because (167*10^3 - 17)/3 = 55661 is prime.
Initial terms and primes associated:
a(1) = 3, 55661;
a(2) = 5, 5566661;
a(3) = 13, 556666666666661;
a(4) = 15, 55666666666666661;
a(5) = 21, 55666666666666666666661; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(167*10^# - 17)/3] &]
CROSSREFS
Sequence in context: A258976 A348659 A137162 * A086769 A018753 A073217
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Oct 18 2017
EXTENSIONS
a(21)-a(23) from Robert Price, Mar 27 2020
STATUS
approved

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Last modified March 29 10:22 EDT 2024. Contains 371268 sequences. (Running on oeis4.)