OFFSET
1,2
COMMENTS
Numbers k such that the digits 33 followed by k-1 occurrences of the digit 6 followed by the digit 1 is prime (see Example section).
a(29) > 2*10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 336w1.
EXAMPLE
2 is in this sequence because (101*10^2 - 17)/3 = 3361 is prime.
Initial terms and associated primes:
a(1) = 1, 331;
a(2) = 2, 3361;
a(3) = 15, 33666666666666661;
a(4) = 17, 3366666666666666661;
a(5) = 26, 3366666666666666666666666661, etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(101*10^# - 17)/3] &]
PROG
(PARI) is(n)=ispseudoprime((101*10^n - 17)/3) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Aug 18 2016
EXTENSIONS
a(27)-a(28) from Robert Price, Feb 05 2020
STATUS
approved