A109907 Beginning with 7, a(n+1) = greatest prime of the form k*{a(n)-k}-1. If no prime is obtained the sequence ends at that point.

7, 11, 29, 197, 9689, 23469167, 137700449916401, 4740353476794815041972197893, 5617737771240172767652929826457529708578746492288409399, 7889744416604625924469156192031986939513870147397674409917489724005347434748024264638497225986334149357868007

Offset: 0

Author

Amarnath Murthy, Jul 15 2005

Keywords

• nonn

Comments

Conjecture: The sequence is infinite.

Crossrefs

Cf. A109904, A109905, A026728, A109908, A109909.

Programs

PARI

{ b(n) = forstep(k=n\2,1,-1,if(isprime(k*(n-k)-1),return(k*(n-k)-1)));return(0) }
my(s=7); while(1,print1(s,", ");s=b(s)) \\ Max Alekseyev, Oct 04 2005

Extensions

More terms from Max Alekseyev, Oct 04 2005