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, 0), (0, -1), (1, 1)}.

A151384

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, 0), (0, -1), (1, 1)}.

Terms

    a(0) =1a(1) =0a(2) =2a(3) =2a(4) =8a(5) =22a(6) =56a(7) =192a(8) =558a(9) =1746a(10) =5850a(11) =18108a(12) =61450a(13) =202310a(14) =672880a(15) =2302762a(16) =7740494a(17) =26610514a(18) =91536712a(19) =315135590a(20) =1097812420a(21) =3815592588a(22) =13349580584a(23) =46872331154a(24) =164755197130a(25) =582028252912

External references