OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 3 followed by k-2 occurrences of the digit 0 followed by the digits 37 is prime (see Example section).
a(30) > 3*10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 30w37.
EXAMPLE
2 is in this sequence because 3*10^2 + 37 = 337 is prime.
Initial terms and associated primes:
a(1) = 1, 67;
a(2) = 2, 337;
a(3) = 3, 3037;
a(4) = 7, 30000037;
a(5) = 9, 3000000037; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[3*10^# + 37] &]
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Oct 23 2017
EXTENSIONS
a(28) from Robert Price, Aug 15 2018
a(29) from Robert Price, Oct 26 2023
STATUS
approved