38013731756domain: NAppears in sequencesNumber of walks on square lattice. Column y=1 of A052174.at n=20A005559a(n) is the number of walks from (0,0) to (0,1) that remain in the upper half-plane y >= 0 using (2*n - 1) unit steps either up (U), down (D), left (L) or right (R).at n=10A145600a(n) = Catalan(n)^2*n.at n=11A268085