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 17 is prime (see Example section).
a(29) > 2*10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 30w17.
EXAMPLE
2 is in this sequence because 3*10^2 + 17 = 317 is prime.
Initial terms and associated primes:
a(1) = 1, 47;
a(2) = 2, 317;
a(3) = 5, 300017;
a(4) = 6, 3000017;
a(5) = 13, 30000000000017; etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[3*10^# + 17] &]
PROG
(PARI) isok(n) = isprime((3*10^n + 17)); \\ Indranil Ghosh, Mar 14 2017
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
Robert Price, Mar 14 2017
EXTENSIONS
a(28) from Robert Price, Jul 27 2018
STATUS
approved