OFFSET
1,1
LINKS
EXAMPLE
F(24) = 46368 = 2^5 * 3^2 * 7 * 23 is composite and the concatenation 2222233723 is prime, so 24 is in the sequence.
CROSSREFS
KEYWORD
nonn,base,hard,more
AUTHOR
EXTENSIONS
More terms from Jens Kruse Andersen, Jan 05 2003
a(17)-a(18) from Ryan Propper, May 29 2006
a(19)-a(20) from Sean A. Irvine, Jan 16 2021
STATUS
approved