Number of ordered pairs (p,q) of permutations of [n] with equal up-down signatures and p(1)=q(1) if n>0.
A262234
Number of ordered pairs (p,q) of permutations of [n] with equal up-down signatures and p(1)=q(1) if n>0.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =6a(4) =36a(5) =376a(6) =6040a(7) =137320a(8) =4188320a(9) =164844064a(10) =8129435904a(11) =490812707456
External references
- oeis: A262234