OFFSET
1,1
COMMENTS
Numbers k such that the digits 49 followed by k occurrences of the digit 3 is prime (see Example section).
a(30) > 2*10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 493w.
EXAMPLE
3 is in this sequence because (148*10^3-1)/3 = 233329 is prime.
Initial terms and associated primes:
a(1) = 2, 4933;
a(2) = 3, 49333;
a(3) = 4, 493333;
a(4) = 5, 4933333;
a(5) = 9, 49333333333, etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(148*10^# - 1)/3] &]
PROG
(PARI) is(n)=ispseudoprime((148*10^n - 1)/3) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Jun 18 2016
EXTENSIONS
a(27)-a(29) from Robert Price, Mar 18 2020
STATUS
approved