

A056725


Numbers k such that 9*10^k  1 is prime.


16



1, 3, 7, 19, 29, 37, 93, 935, 8415, 9631, 11143, 41475, 41917, 48051, 107663, 212903, 223871, 260253, 364521, 383643, 1009567, 1762063
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

Also numbers k such that 8*10^k + 9*R_k is prime, where R_k = 11...1 is the repunit (A002275) of length k.
1009567 is also a member of this sequence, but its position is presently undetermined: 9 * 10^1009567  1 is prime.  Predrag Kurtovic, Sep 19 2016


LINKS



MATHEMATICA

Do[ If[ PrimeQ[ 8*10^n + (10^n1)], Print[n]], {n, 1, 6750, 2}]


PROG



CROSSREFS



KEYWORD

hard,nonn,more


AUTHOR



EXTENSIONS

More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 01 2008


STATUS

approved



