OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 5 followed by k-2 occurrences of the digit 6 followed by the digits 93 is prime (see Example section).
a(30) > 3*10^5. - Robert Price, Jul 10 2023
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 56w93.
EXAMPLE
3 is in this sequence because (17*10^3+79)/3 = 5693 is prime.
Initial terms and associated primes:
a(1) = 1, 83;
a(2) = 2, 593;
a(3) = 3, 5693;
a(4) = 5, 566693;
a(5) = 7, 56666693, etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(17*10^# + 79)/3] &]
PROG
(PARI) is(n)=ispseudoprime((17*10^n + 79)/3) \\ Charles R Greathouse IV, Jun 08 2016
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, May 28 2016
EXTENSIONS
a(28)-a(29) from Robert Price, Apr 15 2019
STATUS
approved