Number of "sets of even lists" for even n, cf. A000262.

A088026

Number of "sets of even lists" for even n, cf. A000262.

Terms

    a(0) =1a(1) =2a(2) =36a(3) =1560a(4) =122640a(5) =15150240a(6) =2695049280a(7) =650948538240

External references