Number of symmetric paths in the first quadrant, from (0,0) to (n,0), consisting of steps U=(1,1), D=(1,-1), h=(1,0) and H=(2,0).

A132887

Number of symmetric paths in the first quadrant, from (0,0) to (n,0), consisting of steps U=(1,1), D=(1,-1), h=(1,0) and H=(2,0).

Terms

    a(0) =1a(1) =1a(2) =3a(3) =2a(4) =8a(5) =6a(6) =23a(7) =17a(8) =68a(9) =51a(10) =205a(11) =154a(12) =627a(13) =473a(14) =1937a(15) =1464a(16) =6032a(17) =4568a(18) =18900a(19) =14332a(20) =59519a(21) =45187a(22) =188211a(23) =143024a(24) =597241a(25) =454217a(26) =1900821a(27) =1446604a(28) =6065180a(29) =4618576

External references