OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 4 followed by k-2 occurrences of the digit 3 followed by the digits 99 is prime (see the Example section).
a(30) > 10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 43w99.
EXAMPLE
4 is in this sequence because (13*10^4 + 197)/3 = 43399 is prime.
Initial terms and associated primes:
a(1) = 1, 109;
a(2) = 2, 499;
a(3) = 4, 43399;
a(4) = 5, 433399;
a(5) = 17, 433333333333333399, etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(13*10^# + 197)/3] &]
PROG
(PARI) is(n)=ispseudoprime((13*10^n+197)/3) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Aug 29 2016
STATUS
approved