694800domain: NAppears in sequencesNumber of (w,x,y,z) with all terms in {0,...,n} and at least one of these conditions holds: w<R, x>R, y>R, z>R, where R = max{w,x,y,z} - min{w,x,y,z}.at n=29A212754a(0) = 1; a(n) = (1/n) * Sum_{k=3..n} (binomial(n,k) * k!)^2 * a(n-k) / k.at n=7A346292