OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 6 followed by k-2 occurrences of the digit 0 followed by the digits 73 is prime (see Example section).
a(27) > 2*10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 60w73.
EXAMPLE
3 is in this sequence because 6*10^3 + 73 = 6073 is prime.
Initial terms and associated primes:
a(1) = 0, 79;
a(2) = 2, 673;
a(3) = 3, 6073;
a(4) = 5, 600073;
a(5) = 6, 6000073; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[6*10^# + 73] &]
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Apr 29 2017
EXTENSIONS
a(25)-a(26) from Robert Price, Apr 04 2019
STATUS
approved