Number of lattice paths from (0,0) to (n,n) using steps (1,0), (0,1), (1,1), (-1,1) and whose points lie entirely in the integer square of lattice points {(i,j): 0 <= i,j <= n}.

A339654

Number of lattice paths from (0,0) to (n,n) using steps (1,0), (0,1), (1,1), (-1,1) and whose points lie entirely in the integer square of lattice points {(i,j): 0 <= i,j <= n}.