a(n) is the number of walks from (0,0) to (0,2) that remain in the upper half-plane y >= 0 using 2*n unit steps either up (U), down (D), left (L) or right (R).
A145601
a(n) is the number of walks from (0,0) to (0,2) that remain in the upper half-plane y >= 0 using 2*n unit steps either up (U), down (D), left (L) or right (R).
Terms
- a(0) =1a(1) =15a(2) =189a(3) =2352a(4) =29700a(5) =382239a(6) =5010005a(7) =66745536a(8) =901995588a(9) =12342120700a(10) =170724392916
External references
- oeis: A145601