Number of weighted lattice paths in B(n) having no valleys. The members of B(n) are paths of weight n that start at (0,0), end on but never go below the horizontal axis, and whose steps are of the following four kinds: an (1,0)-step with weight 1, an (1,0)-step with weight 2, a (1,1)-step with weight 2, and a (1,-1)-step with weight 1. The weight of a path is the sum of the weights of its steps. A valley is a (1,-1)-step followed by a (1,1)-step.
A182901
Number of weighted lattice paths in B(n) having no valleys. The members of B(n) are paths of weight n that start at (0,0), end on but never go below the horizontal axis, and whose steps are of the following four kinds: an (1,0)-step with weight 1, an (1,0)-step with weight 2, a (1,1)-step with weight 2, and a (1,-1)-step with weight 1. The weight of a path is the sum of the weights of its steps. A valley is a (1,-1)-step followed by a (1,1)-step.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =4a(4) =8a(5) =17a(6) =36a(7) =78a(8) =171a(9) =379a(10) =848a(11) =1912a(12) =4341a(13) =9915a(14) =22767a(15) =52526a(16) =121698a(17) =283043a(18) =660579a(19) =1546556a(20) =3631261a(21) =8548643a(22) =20174093a(23) =47716388a(24) =113095740a(25) =268575321a(26) =638954183a(27) =1522668500a(28) =3634346039a(29) =8687404327
External references
- oeis: A182901