OFFSET
1,3
COMMENTS
Also numbers k such that (4*10^k + 23)/9 is prime.
a(14) > 10^5. - Robert Price, Nov 26 2014
LINKS
FORMULA
a(n) = A056682(n-1) + 1. - Robert Price, Nov 26 2014
MATHEMATICA
Do[ If[ PrimeQ[ 4(10^n - 1)/9 + 3], Print[n]], {n, 5000}]
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Robert G. Wilson v, Oct 14 2004
EXTENSIONS
a(11)-a(13) from Robert Price, Nov 26 2014
a(14)-a(15) from Kamada data by Tyler Busby, May 03 2024
STATUS
approved