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), (-1, 1), (0, -1), (1, 0)}.
A151499
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), (-1, 1), (0, -1), (1, 0)}.
Terms
- a(0) =1a(1) =0a(2) =1a(3) =1a(4) =4a(5) =5a(6) =20a(7) =47a(8) =126a(9) =327a(10) =1041a(11) =2854a(12) =8083a(13) =24892a(14) =76208a(15) =222509a(16) =686079a(17) =2174516a(18) =6673802a(19) =20646366a(20) =66232829a(21) =210542762a(22) =662048460a(23) =2129820354a(24) =6910328426a(25) =22163635347a(26) =71624432296a(27) =234661293959a(28) =765583825870
External references
- oeis: A151499