cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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.

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%I A092969 #8 Mar 14 2015 18:32:59
%S A092969 2,3,7,13,61,241,2521,20161,72577,604801,39916801,59875201,3113510401,
%T A092969 17435658241,186810624001,10461394944001,118562476032001,0,
%U A092969 24329020081766401,304112751022080001,12772735542927360001
%N 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.
%C A092969 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.
%C A092969 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
%H A092969 Vincenzo Librandi, <a href="/A092969/b092969.txt">Table of n, a(n) for n = 1..200</a>
%t A092969 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 *)
%o A092969 (PARI) a(n)=for (i=1,n,if(isprime(n!/i+1),return((n!/i+1))))
%Y A092969 Cf. A092968, A092970.
%K A092969 nonn
%O A092969 1,1
%A A092969 _Amarnath Murthy_, Mar 26 2004
%E A092969 More terms from Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 26 2004