OFFSET
1,3
COMMENTS
For k > 1, numbers k such that the digit 6 followed by k-2 occurrences of the digit 0 followed by the digits 37 is prime (see Example section).
a(28) > 2*10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 60w37.
EXAMPLE
3 is in this sequence because 6*10^3 + 37 = 6037 is prime.
Initial terms and associated primes:
a(1) = 0, 43;
a(2) = 1, 97;
a(3) = 3, 6037;
a(4) = 4, 60037;
a(5) = 10, 60000000037; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[6*10^# + 37] &]
PROG
(PARI) isok(k) = isprime(6*10^k + 37); \\ Michel Marcus, Dec 10 2018
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Feb 01 2017
STATUS
approved