Number of walks of length n on square lattice, starting at origin, staying in first quadrant.

A005566

Number of walks of length n on square lattice, starting at origin, staying in first quadrant.

Terms

    a(0) =1a(1) =2a(2) =6a(3) =18a(4) =60a(5) =200a(6) =700a(7) =2450a(8) =8820a(9) =31752a(10) =116424a(11) =426888a(12) =1585584a(13) =5889312a(14) =22084920a(15) =82818450a(16) =312869700a(17) =1181952200a(18) =4491418360a(19) =17067389768a(20) =65166397296a(21) =248817153312a(22) =953799087696

External references