Number of lattice paths from (0,0) to (n,0) that do not go below the x-axis or above the diagonal x=y and consist of steps U=(1,1), D=(1,-1), H=(1,0) and S=(0,1).

A225041

Number of lattice paths from (0,0) to (n,0) that do not go below the x-axis or above the diagonal x=y and consist of steps U=(1,1), D=(1,-1), H=(1,0) and S=(0,1).

Terms

    a(0) =1a(1) =1a(2) =3a(3) =9a(4) =35a(5) =145a(6) =659a(7) =3137a(8) =15619a(9) =80177a(10) =422595a(11) =2273633a(12) =12447667a(13) =69138193a(14) =388784259a(15) =2209440945a(16) =12671782579a(17) =73260414481a(18) =426545078627

External references