Number of paths in the first quadrant from (0,0) to (n,0) using steps U=(1,1), D=(1,-1), h=(1,0) and H=(2,0).

A128720

Number of paths in the first quadrant from (0,0) to (n,0) using steps U=(1,1), D=(1,-1), h=(1,0) and H=(2,0).

Terms

    a(0) =1a(1) =1a(2) =3a(3) =6a(4) =16a(5) =40a(6) =109a(7) =297a(8) =836a(9) =2377a(10) =6869a(11) =20042a(12) =59071a(13) =175453a(14) =524881a(15) =1579752a(16) =4780656a(17) =14536878a(18) =44394980a(19) =136107872a(20) =418757483a(21) =1292505121a(22) =4001039563a(23) =12418772656a(24) =38641790001a(25) =120510911885a(26) =376628460529

External references