OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digits 16 followed by k-1 occurrences of the digit 0 followed by the digit 1 is prime (see Example section).
a(31) > 10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 160w1.
EXAMPLE
4 is in this sequence because 16*10^4+1 = 160001 is prime.
Initial terms and associated primes:
a(1) = 0, 17;
a(2) = 2, 1601;
a(3) = 3, 16001;
a(4) = 4, 160001;
a(5) = 18, 16000000000000000001. etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[16*10^#+1] &]
PROG
(PARI) is(n)=ispseudoprime(16*10^n+1) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, May 12 2016
STATUS
approved