610351562500domain: NAppears in sequencesa(0) = 1; a(n) = 4*5^(n-1) for n >= 1.at n=17A005054a(n+1) = floor(a(n)/2) * ceiling(a(n)/2), a(0) = 5.at n=7A014980a(1)=5. For n > 1, a(n) = 4*5^(n-1) = A005054(n).at n=16A110595a(n) = denominators of n!/10^n.at n=20A240534