A110056 Least prime that ends a complete Cunningham chain (of the first kind) of length n.

13, 7, 167, 4079, 47, 2879, 71850239, 2444789759, 21981381119, 13357981992959, 681004115066879, 1136001594224639, 16756459239477534719, 781558105952602767359

Offset: 1

Author

Alexandre Wajnberg, Sep 04 2005

Keywords

• nonn
• hard

Comments

"Complete" means that this chain is not part of a longer Cunningham chain of the first kind.

Next term is greater than 4*10^17.

A005602(13)-> 8181864863026139 -> ... -> a(13) = 16756459239477534719. [From Washington Bomfim, Oct 21 2009]

Examples

			41->83->167 is a Cunningham chain of the first kind. It is complete because neither (41-1)/2 nor 2*167+1 is prime. It is the first such chain of three primes, so a(3) = 167.
		

Links

• Chris Caldwell's Prime Glossary, Cunn ingham chains.

Crossrefs

Cf. A005384, A005385, A007700, A023272, A023302, A023330, A059452, A057326, A059455, A059761, A059762, A059763, A059764, A074313.

Cf. A110059 for Cunningham chains of the second kind.

Cf. A005602 [From Washington Bomfim, Oct 21 2009]

Extensions

Edited and extended by David Wasserman, Aug 08 2006

a(13) and a(14) from Washington Bomfim, Oct 21 2009