OFFSET
1,2
COMMENTS
For k > 1, numbers k such that k-2 occurrences of the digit 3 followed by the digits 59 is prime (see Example section).
a(34) > 2*10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 3w59.
EXAMPLE
3 is in this sequence because (10^3 + 77)/3 = 359 is prime.
Initial terms and associated primes:
a(1) = 1, 29;
a(2) = 2, 59;
a(3) = 3, 359;
a(4) = 4, 3359;
a(5) = 5, 33359; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(10^# + 77)/3] &]
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Jan 21 2017
EXTENSIONS
a(31)-a(33) from Robert Price, Jan 18 2018
STATUS
approved