Voozh

A092969

a(1) = 2; for n>1, a(n) = largest prime of the form n!/k + 1, where k < n, or 0 if no such prime exists.

2, 3, 7, 13, 61, 241, 2521, 20161, 72577, 604801, 39916801, 59875201, 3113510401, 17435658241, 186810624001, 10461394944001, 118562476032001, 0, 24329020081766401, 304112751022080001, 12772735542927360001

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OFFSET

1,1

COMMENTS

Conjecture: There are only finitely many zeros in this sequence. In other words the sequence is identical to A092965 barring a finite set of terms which are zero.

I found zeros for n: 18,51,53,84,95,100,104,106,143,178,180,181,188,202,203,(204). - Robert G. Wilson v, Mar 27 2004

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..200

MATHEMATICA

f[n_] := Block[{k = 1}, While[ !PrimeQ[n!/k + 1], k++ ]; If[k < n, n!/k + 1, 0]]; Table[ f[n], {n, 22}] (* Robert G. Wilson v, Mar 27 2004 *)

PROG

(PARI) a(n)=for (i=1, n, if(isprime(n!/i+1), return((n!/i+1))))

CROSSREFS

Cf. A092968, A092970.

Sequence in context: A104367 A104365 A104372 * A089136 A092965 A051454

Adjacent sequences: A092966 A092967 A092968 * A092970 A092971 A092972

KEYWORD