Number of walks in the first quadrant starting and ending at (0,0) consisting of 3n steps taken from {E=(1, 0), D=(-1, 1), S=(0, -1)}, no S step occurring before the final E step.
A274969
Number of walks in the first quadrant starting and ending at (0,0) consisting of 3n steps taken from {E=(1, 0), D=(-1, 1), S=(0, -1)}, no S step occurring before the final E step.
Terms
- a(0) =1a(1) =1a(2) =4a(3) =21a(4) =121a(5) =728a(6) =4488a(7) =28101a(8) =177859a(9) =1134705a(10) =7283640a(11) =46981740a(12) =304253964a(13) =1976886616a(14) =12880883408a(15) =84130964709a(16) =550649378199
External references
- oeis: A274969