OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 8 followed by k-2 occurrences of the digit 3 followed by the digits 53 is prime (see Example section).
a(29) > 2*10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 83w53.
EXAMPLE
3 is in this sequence because (25*10^3+59)/3 = 8353 is prime.
Initial terms and associated primes:
a(1) = 1, 103;
a(2) = 2, 853;
a(3) = 3, 8353;
a(4) = 5, 833353;
a(5) = 6, 83333353, etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(25*10^# + 59)/3] &]
PROG
(PARI) is(n)=ispseudoprime((25*10^n + 59)/3) \\ Charles R Greathouse IV, Jun 08 2016
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, May 28 2016
STATUS
approved