Number of 5 up, 5 down, 5 up, ... permutations of length 5n+1.

A259452

Number of 5 up, 5 down, 5 up, ... permutations of length 5n+1.

Terms

    a(0) =1a(1) =1a(2) =252a(3) =578005a(4) =6190034016

External references