OFFSET
1,1
COMMENTS
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..1000
Chris Caldwell's Prime Glossary, Cunningham chains.
EXAMPLE
89 is a term because (89-1)/2 = 44 and 64*89+63 = 5759 = 13*443 are composites, while 89, 179, 359, 719, 1439, and 2879 are primes.
1122659 is not a term because it initiates a chain of length 7.
4658939 is not a term because (4658939-1)/2 = 2329469 is prime. - Sean A. Irvine, Oct 09 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Feb 21 2001
EXTENSIONS
Entry revised by N. J. A. Sloane Apr 01 2006
a(12) onward corrected and extended by Sean A. Irvine, Oct 09 2022
STATUS
approved