OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 4 followed by k-2 occurrences of the digit 0 followed by the digits 93 is prime (see Example section).
a(30) > 2*10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 40w93.
EXAMPLE
4 is in this sequence because 4*10^4 + 93 = 40093 is prime.
Initial terms and associated primes:
a(1) = 0, 97;
a(2) = 3, 4093;
a(3) = 4, 40093;
a(4) = 5, 400093;
a(5) = 6, 4000093; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[4*10^# + 93] &]
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Jan 31 2017
EXTENSIONS
a(28)-a(29) from Robert Price, Aug 13 2018
STATUS
approved