Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0) and consisting of n steps taken from {(-1, 0), (0, -1), (0, 1), (1, -1)}.

A151262

Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0) and consisting of n steps taken from {(-1, 0), (0, -1), (0, 1), (1, -1)}.

Terms

    a(0) =1a(1) =1a(2) =3a(3) =6a(4) =18a(5) =47a(6) =141a(7) =416a(8) =1278a(9) =3983a(10) =12616a(11) =40475a(12) =131461a(13) =430548a(14) =1423924a(15) =4741118a(16) =15896509a(17) =53622384a(18) =181826538a(19) =619678461a(20) =2121171010a(21) =7290531452a(22) =25152947775a(23) =87076167883a(24) =302422286268

External references