Number of site swap patterns with 4 balls and exact period n.

A065180

Number of site swap patterns with 4 balls and exact period n.

Terms

    a(0) =1a(1) =4a(2) =20a(3) =90a(4) =420a(5) =1910a(6) =8820a(7) =40590a(8) =187880a(9) =871494a(10) =4057620a(11) =18945960a(12) =88738020a(13) =416787030a(14) =1962922276a(15) =9268287390a(16) =43868210820a(17) =208109782580a(18) =989400443220

External references