Number of paths from (0,0) to (3n,0) that stay in the first quadrant (x,y >= 0) and where each step is (3,0), (2,1), (1,2), or (1,-1).

A107708

Number of paths from (0,0) to (3n,0) that stay in the first quadrant (x,y >= 0) and where each step is (3,0), (2,1), (1,2), or (1,-1).

Terms

    a(0) =1a(1) =3a(2) =18a(3) =144a(4) =1323a(5) =13176a(6) =138348a(7) =1507977a(8) =16900650a(9) =193536864a(10) =2254630788a(11) =26635735440a(12) =318350663748

External references