OFFSET
1,1
COMMENTS
Also numbers k such that (5*10^k + 31)/9 is prime.
LINKS
FORMULA
a(n) = A056687(n) + 1.
MATHEMATICA
Do[ If[ PrimeQ[ 5(10^n - 1)/9 + 4], Print[n]], {n, 0, 5000}]
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Robert G. Wilson v, Oct 14 2004
EXTENSIONS
a(13)-a(15) from Kamada link by Ray Chandler, Feb 27 2012
a(16)-a(17) from Kamada data by Tyler Busby, May 03 2024
STATUS
approved