OFFSET
0,5
COMMENTS
a(n) = n! * P(floor(n/2))/P(n), where P(n) is a primorial number (A034386).
MAPLE
A182922 := n -> n! / mul(k, k=select(isprime, [$iquo(n, 2)+1..n])):
# Or without division:
a182922 := proc(n) local k, i, R;
R := {seq(i, i=1..n)} minus {op(select(isprime, [seq(i, i=iquo(n, 2)+1..n)]))};
mul(k, k=R) end:
MATHEMATICA
a[n_] := n!/Numerator[n!/Floor[n/2]!^4];
Table[a[n], {n, 0, 22}] (* Jean-François Alcover, Jun 18 2019 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Mar 05 2011
STATUS
approved