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, 1)}.

A151398

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, 1)}.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =4a(4) =11a(5) =26a(6) =84a(7) =220a(8) =742a(9) =2070a(10) =7197a(11) =20922a(12) =74432a(13) =223010a(14) =805708a(15) =2470392a(16) =9027576a(17) =28187178a(18) =103920850a(19) =329292906a(20) =1222553336a(21) =3921481206a(22) =14641490905a(23) =47450199350a(24) =177987479208a(25) =581924348298

External references