Number of positive walks with n steps {-2,-1,0,1,2} starting at the origin, ending at altitude 2, and staying strictly above the x-axis.

A276903

Number of positive walks with n steps {-2,-1,0,1,2} starting at the origin, ending at altitude 2, and staying strictly above the x-axis.

Terms

    a(0) =0a(1) =1a(2) =2a(3) =7a(4) =25a(5) =96a(6) =382a(7) =1567a(8) =6575a(9) =28096a(10) =121847a(11) =534953a(12) =2373032a(13) =10619922a(14) =47890013a(15) =217395690a(16) =992640367a(17) =4555957948a(18) =21007405327a(19) =97266928685a(20) =452046424465

External references