2097682domain: NAppears in sequencesNumber of (3+1) X (n+1) 0..1 arrays with nondecreasing x(i,j)-x(i,j-1) in the i direction and nondecreasing absolute value of x(i,j)-x(i-1,j) in the j direction.at n=17A250771a(n) = Sum_{k=1..floor(sqrt(n))} 2^floor(n/k-k).at n=22A360303