303898domain: NAppears in sequencesa(0) = 0, a(1) = 1 and for n >= 2, a(n) = floor(2 * sqrt(a(n-2) * a(n-1))).at n=30A093333Number of nX3 0..1 arrays with every element equal to 0, 1, 3 or 4 horizontally, vertically or antidiagonally adjacent elements, with upper left element zero.at n=22A300501