Triangle of numbers of square lattice walks that start and end at origin after 2k steps and contain exactly r steps to the east, not touching origin at intermediate stages.

A068218

Triangle of numbers of square lattice walks that start and end at origin after 2k steps and contain exactly r steps to the east, not touching origin at intermediate stages.

Terms

    a(0) =1a(1) =2a(2) =2a(3) =2a(4) =16a(5) =2a(6) =4a(7) =84a(8) =84a(9) =4a(10) =10a(11) =400a(12) =1056a(13) =400a(14) =10a(15) =28a(16) =1820a(17) =9184a(18) =9184a(19) =1820a(20) =28a(21) =84a(22) =8064a(23) =66276a(24) =126720a(25) =66276a(26) =8064a(27) =84a(28) =264a(29) =35112

External references