Number of paths from (0,0) to (3n,0) that stay in first quadrant (but may touch horizontal axis), where each step is (2,1),(1,2) or (1,-1) and start with (2,1).

A032349

Number of paths from (0,0) to (3n,0) that stay in first quadrant (but may touch horizontal axis), where each step is (2,1),(1,2) or (1,-1) and start with (2,1).

Terms

    a(0) =1a(1) =4a(2) =24a(3) =172a(4) =1360a(5) =11444a(6) =100520a(7) =911068a(8) =8457504a(9) =80006116a(10) =768464312a(11) =7474561164a(12) =73473471344a(13) =728745517972

External references