For n people on one side of a river, the number of ways they can all travel to the opposite side following the pattern of 2 sent, 1 returns, 2 sent, 1 returns, ..., 2 sent.

A167484

For n people on one side of a river, the number of ways they can all travel to the opposite side following the pattern of 2 sent, 1 returns, 2 sent, 1 returns, ..., 2 sent.

Terms

    a(0) =1a(1) =1a(2) =6a(3) =108a(4) =4320a(5) =324000a(6) =40824000a(7) =8001504000

External references