Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0) and consisting of n steps taken from {(-1, -1), (-1, 0), (0, 1), (1, -1)}.
A151257
Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0) and consisting of n steps taken from {(-1, -1), (-1, 0), (0, 1), (1, -1)}.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =4a(4) =11a(5) =26a(6) =70a(7) =195a(8) =558a(9) =1578a(10) =4678a(11) =14067a(12) =42248a(13) =128588a(14) =399183a(15) =1241119a(16) =3873090a(17) =12243222a(18) =38947570a(19) =124009672a(20) =397559401a(21) =1283652201a(22) =4152226324a(23) =13472767649a(24) =43967385684a(25) =143918657309a(26) =471891799395
External references
- oeis: A151257