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), (1, -1), (1, 0)}.
A151503
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), (1, -1), (1, 0)}.
Terms
- a(0) =1a(1) =0a(2) =1a(3) =1a(4) =3a(5) =6a(6) =17a(7) =40a(8) =117a(9) =314a(10) =912a(11) =2667a(12) =7916a(13) =23963a(14) =73586a(15) =227611a(16) =715444a(17) =2262450a(18) =7223397a(19) =23261164a(20) =75343490a(21) =245847919a(22) =806839587a(23) =2661738663a(24) =8829581024a(25) =29418789715a(26) =98457806482a(27) =330890849398
External references
- oeis: A151503