OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 8 followed by k-2 occurrences of the digit 4 followed by the digits 63 is prime (see Example section).
a(27) > 10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 84w63.
EXAMPLE
4 is in this sequence because (76*10^4+167)/9 = 84463 is prime.
Initial terms and associated primes:
a(1) = 1, 103;
a(2) = 2, 863;
a(3) = 4, 84463;
a(4) = 5, 844463;
a(5) = 7, 84444463, etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(76*10^#+167)/9] &]
PROG
(PARI) is(n)=ispseudoprime((76*10^n+167)/9) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Aug 09 2016
STATUS
approved