A270838 - OEIS

%I #8 Mar 01 2020 16:44:45

%S 1,1,1,1,11,1,11,10,15,1,1,1,1,37,29,52,48,35,55,1,46,67,53,1,96,53,

%T 22,1,1,1,120,122,123,75,1,1,83,1,1,1,1,90,1,117,105,111,82,1,168,119,

%U 1,125,1,1,1,135,236,1,141,1,153,281,1,1,231,1,1,1,1,236

%N Largest value k < p-2 such that k! mod p = 1 with p = prime(n).

%H Alois P. Heinz, <a href="/A270838/b270838.txt">Table of n, a(n) for n = 3..4555</a>

%p a:= proc(n) option remember; local k, p; p:=ithprime(n);

%p       for k from p-3 by -1 do if irem(k!, p)=1 then return k fi od

%p     end:

%p seq(a(n), n=3..100);

%t lvk[n_]:=Module[{p=Prime[n],k},k=p-3;While[Mod[k!,p]!=1,k--];k]; Array[ lvk,80,3] (* _Harvey P. Dale_, Mar 01 2020 *)

%Y Cf. A000040, A270780.

%K nonn

%O 3,5

%A _Alois P. Heinz_, Mar 23 2016