Triangle of numbers of walks in the quarter-plane, of length 2n beginning and ending at the origin using steps {(1,1), (1,0), (-1,0), (-1,-1)} (Gessel steps) arranged according to the number of times the steps (1,1) and (-1,-1) occur.
A157513
Triangle of numbers of walks in the quarter-plane, of length 2n beginning and ending at the origin using steps {(1,1), (1,0), (-1,0), (-1,-1)} (Gessel steps) arranged according to the number of times the steps (1,1) and (-1,-1) occur.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =2a(4) =7a(5) =2a(6) =5a(7) =37a(8) =38a(9) =5a(10) =14a(11) =177a(12) =390a(13) =187a(14) =14a(15) =42a(16) =806a(17) =3065a(18) =3175a(19) =874a(20) =42a(21) =132a(22) =3566a(23) =20742a(24) =37260a(25) =22254a(26) =3958a(27) =132a(28) =429a(29) =15485
External references
- oeis: A157513