Number of "ups" and "downs" in the permutations of [n] if either a previous counted "up" ("down") or a "void" precedes an "up" ("down") which then will be counted also.
A120928
Number of "ups" and "downs" in the permutations of [n] if either a previous counted "up" ("down") or a "void" precedes an "up" ("down") which then will be counted also.
Terms
- a(0) =2a(1) =8a(2) =44a(3) =280a(4) =2040a(5) =16800a(6) =154560a(7) =1572480a(8) =17539200a(9) =212889600a(10) =2794176000a(11) =39437798400a(12) =595718323200
External references
- oeis: A120928