A109907 - OEIS

%I #11 Dec 31 2024 15:39:04

%S 7,11,29,197,9689,23469167,137700449916401,

%T 4740353476794815041972197893,

%U 5617737771240172767652929826457529708578746492288409399,7889744416604625924469156192031986939513870147397674409917489724005347434748024264638497225986334149357868007

%N 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.

%C Conjecture: The sequence is infinite.

%o (PARI) { b(n) = forstep(k=n\2,1,-1,if(isprime(k*(n-k)-1),return(k*(n-k)-1)));return(0) }

%o my(s=7); while(1,print1(s,", ");s=b(s)) \\ _Max Alekseyev_, Oct 04 2005

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

%K nonn

%O 0,1

%A _Amarnath Murthy_, Jul 15 2005

%E More terms from _Max Alekseyev_, Oct 04 2005