OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 8 followed by k-2 occurrences of the digit 6 followed by the digits 59 is prime (see Example section).
a(31) > 2*10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 86w59.
EXAMPLE
2 is in this sequence because (26*10^2 - 23)/3 = 859 is prime.
Initial terms and associated primes:
a(1) = 1, 79;
a(2) = 2, 859;
a(3) = 10, 86666666659;
a(4) = 16, 86666666666666659, etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(26*10^# - 23)/3] &]
PROG
(PARI) is(n)=ispseudoprime((26*10^n - 23)/3) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Aug 17 2016
EXTENSIONS
a(30) from Robert Price, Dec 19 2019
STATUS
approved