OFFSET
6,1
COMMENTS
From Robert Israel, Jun 26 2020: (Start)
If n is prime, (n-1)!/n is not an integer and a(n) is taken to be 0.
If n = 2*p where p is an odd prime, a(n) = (2*p-1)!/(2*p!). (End)
LINKS
Robert Israel, Table of n, a(n) for n = 6..733
EXAMPLE
a(9) = 20160/9 = 2240.
MAPLE
f:= proc(n) local t, v, k;
if isprime(n) then return 0 fi;
t:= (n-1)!/n;
for k from 1 do
v:= t/k;
if not v::integer then return t fi;
t:= v;
od
end proc:
map(f, [$6..40]); # Robert Israel, Jun 26 2020
MATHEMATICA
a[n_] := Module[{P, r}, For[r = 1, True, r++, P = (n-r)* Pochhammer[n-r+1, r]/n; If[Divisible[P, n], Return[P/n]]]];
Table[a[n], {n, 6, 40}] (* Jean-François Alcover, Feb 07 2023 *)
PROG
(PARI) m=34; for(n=6, m, r=1; p=n-r; while(r<=n&&p%n>0, r++; p=p*(n-r)); print1(p/n, ", "))
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Amarnath Murthy, Mar 16 2004
EXTENSIONS
More terms from Klaus Brockhaus, Mar 17 2004
STATUS
approved