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, 0), (0, -1), (0, 1), (1, -1)}.
A151404
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, 0), (0, -1), (0, 1), (1, -1)}.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =4a(4) =9a(5) =23a(6) =58a(7) =160a(8) =447a(9) =1280a(10) =3799a(11) =11329a(12) =34648a(13) =107194a(14) =335052a(15) =1062809a(16) =3392928a(17) =10944072a(18) =35576811a(19) =116369798a(20) =383517144a(21) =1270497711a(22) =4232708951a(23) =14174190320a(24) =47670133454a(25) =161055621043a(26) =546226400383
External references
- oeis: A151404