Number of even parity alternating permutations of [1..n] starting with an odd integer.

A364849

Number of even parity alternating permutations of [1..n] starting with an odd integer.

Terms

    a(0) =1a(1) =1a(2) =1a(3) =1a(4) =2a(5) =6a(6) =18a(7) =72a(8) =288a(9) =1440a(10) =7200a(11) =43200a(12) =259200a(13) =1814400a(14) =12700800a(15) =101606400a(16) =812851200a(17) =7315660800a(18) =65840947200a(19) =658409472000

External references