OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 9 followed by k-2 occurrences of the digit 1 followed by the digits 29 is prime (see Example section).
a(32) > 2*10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 91w29.
EXAMPLE
4 is in this sequence because (82*10^4+161)/9 = 91129 is prime.
Initial terms and associated primes:
a(1) = 1, 109;
a(2) = 2, 929;
a(3) = 4, 91129;
a(4) = 5, 911129;
a(5) = 7, 91111129, etc.
MATHEMATICA
Select[Range[0, 100000], PrimeQ[(82*10^# + 161)/9] &]
PROG
(PARI) is(n)=ispseudoprime((82*10^n + 161)/9) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Apr 08 2016
EXTENSIONS
a(31) from Robert Price, Oct 31 2019
STATUS
approved