OFFSET
1,3
COMMENTS
For k > 1, numbers k such that the digits 88 followed by k-1 occurrences of the digit 6 followed by the digit 1 is prime (see Example section).
a(38) > 3*10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 886w1.
EXAMPLE
3 is in this sequence because (266*10^3-17)/3 = 88661 is prime.
Initial terms and associated primes:
a(1) = 0, 83;
a(2) = 1, 881;
a(3) = 2, 8861;
a(4) = 3, 88661;
a(5) = 7, 886666661, etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(266*10^# - 17)/3] &]
PROG
(PARI) isok(n) = isprime((266*10^n - 17)/3); \\ Michel Marcus, Jun 18 2016
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Jun 17 2016
EXTENSIONS
a(32)-a(36) from Robert Price, Jul 16 2020
a(37) from Robert Price, Jun 21 2023
STATUS
approved