2 up, 2 down, ..., 2 up, 2 down permutations of length 4n+1.

A131453

2 up, 2 down, ..., 2 up, 2 down permutations of length 4n+1.

Terms

    a(0) =1a(1) =6a(2) =1456a(3) =2020656a(4) =9336345856

External references