|
%I #5 Jan 15 2019 16:18:58
%S 2,2,3,7,31,181,1009,13441,45361,453601,3991681,39916801,566092801,
%T 10897286401,130767436801,2988969984001,25406244864001,0,
%U 8109673360588801,304112751022080001,2688996956405760001
%N Smallest prime of the form n!/k + 1. k < = n, or 0 if no such prime exists.
%e a(10) = 453601 = 10!/8 + 1, as 10!/10 + 1 and 10!/9 + 1 are both composite.
%t Table[SelectFirst[Reverse[n!/Range[n]+1],PrimeQ],{n,30}]/.(Missing[ "NotFound"] -> 0) (* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jan 15 2019 *)
%o (PARI) a(n)=for (i=1,n,if(isprime(n!/(n-i+1)+1),return((n!/(n-i+1)+1))))
%Y Cf. A092968, A092969, A092068.
%K nonn
%O 1,1
%A _Amarnath Murthy_, Mar 26 2004
%E Corrected and extended by Mohammed Bouayoun (bouyao(AT)wanadoo.fr), Mar 26 2004
|
