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

0,1

Comments

Conjecture: The sequence is infinite.

Links

Table of n, a(n) for n=0..9.

Prog

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

Crossrefs

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

Sequence in context: A045461 A153867 A153325 * A121534 A083363 A027707

Adjacent sequences: A109904 A109905 A109906 * A109908 A109909 A109910

Keyword

nonn

Author

Amarnath Murthy, Jul 15 2005

Extensions

More terms from Max Alekseyev, Oct 04 2005

Status

approved