Number of walks within N^2 (the first quadrant of Z^2) starting and ending at (0,0) and consisting of n steps taken from {(-1, 0), (-1, 1), (0, -1), (1, 0)}.
A151346
Number of walks within N^2 (the first quadrant of Z^2) starting and ending at (0,0) and consisting of n steps taken from {(-1, 0), (-1, 1), (0, -1), (1, 0)}.
Terms
- a(0) =1a(1) =0a(2) =1a(3) =1a(4) =2a(5) =7a(6) =10a(7) =38a(8) =89a(9) =229a(10) =752a(11) =1873a(12) =6009a(13) =17746a(14) =51970a(15) =168199a(16) =503489a(17) =1609327a(18) =5131184a(19) =16183314a(20) =53017947a(21) =170708648a(22) =559207257a(23) =1846295302a(24) =6075728984a(25) =20284263554a(26) =67649481468a(27) =226890912838a(28) =765669449228
External references
- oeis: A151346