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A293000 Numbers k such that (2*10^k - 23)/3 is prime. 0
2, 3, 4, 26, 44, 58, 73, 88, 211, 244, 1393, 2282, 4108, 6777, 7480, 14369, 16153, 21081, 24308, 27368, 43455, 51597, 55559, 67405, 88112, 148460, 288371, 297488 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
For k>1, numbers k-2 occurrences of the digit 6 followed by the digits 59 is prime (see Example section).
a(29) > 3*10^5.
LINKS
Makoto Kamada, Search for 6w59
EXAMPLE
4 is in this sequence because (2*10^4 - 23)/3 = 6659 is prime.
Initial terms and associated primes:
a(1) = 2, 59;
a(2) = 3, 659;
a(3) = 4, 6659;
a(4) = 26, 66666666666666666666666659;
a(5) = 44, 66666666666666666666666666666666666666666659; etc.
MATHEMATICA
Select[Range[1, 100000], PrimeQ[(2*10^# - 23)/3] &]
CROSSREFS
Sequence in context: A171558 A044906 A255312 * A141565 A098549 A274677
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Sep 27 2017
EXTENSIONS
a(26) from Robert Price, Apr 24 2018
a(27)-a(28) from Robert Price, Jun 01 2023
STATUS
approved

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Last modified April 21 03:36 EDT 2024. Contains 371850 sequences. (Running on oeis4.)