Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0), ending on the vertical axis and consisting of n steps taken from {(-1, 1), (0, -1), (0, 1), (1, 0)}.
A151412
Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0), ending on the vertical axis and consisting of n steps taken from {(-1, 1), (0, -1), (0, 1), (1, 0)}.
Terms
- a(0) =1a(1) =1a(2) =3a(3) =7a(4) =21a(5) =63a(6) =198a(7) =648a(8) =2148a(9) =7303a(10) =25159a(11) =87771a(12) =309885a(13) =1103217a(14) =3961285a(15) =14322270a(16) =52098790a(17) =190586734a(18) =700547511a(19) =2586505466a(20) =9587737311a(21) =35667671240a(22) =133128177959a(23) =498385063314
External references
- oeis: A151412