OFFSET
1,2
COMMENTS
For k > 1, numbers k such that the digit 9 followed by k-2 occurrences of the digit 3 followed by the digits 01 is prime (see Example section).
a(30) > 10^5.
LINKS
Makoto Kamada, Factorization of near-repdigit-related numbers.
Makoto Kamada, Search for 93w01.
EXAMPLE
5 is in this sequence because (28*10^5-97)/3 = 877 is prime.
Initial terms and associated primes:
a(1) = 1, 61;
a(2) = 5, 933301;
a(3) = 8, 933333301;
a(4) = 20, 933333333333333333301;
a(5) = 27, 9333333333333333333333333301, etc.
MATHEMATICA
Select[Range[0, 100], PrimeQ[(28*10^#-97)/3 && # > 0] &] (* Corrected by Georg Fischer, Jul 22 2019 *)
PROG
(PARI) is(n)=ispseudoprime((28*10^n-97)/3) \\ Charles R Greathouse IV, Jul 21 2016
(Magma) [n: n in [1..500] | IsPrime((28*10^n-97) div 3)]; // Vincenzo Librandi, Jul 21 2016
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert Price, Jul 20 2016
STATUS
approved