Number of planar walks starting at (1,1), ending at (3n,0), remaining in the first quadrant and using steps (-1,2) and (2,-1).

A277248

Number of planar walks starting at (1,1), ending at (3n,0), remaining in the first quadrant and using steps (-1,2) and (2,-1).

Terms

    a(0) =1a(1) =2a(2) =6a(3) =24a(4) =108a(5) =528a(6) =2724a(7) =14616a(8) =80760a(9) =456552a(10) =2628504a(11) =15360216a(12) =90879096a(13) =543336912a(14) =3277586136a(15) =19924733088a(16) =121943223576a(17) =750756116376

External references