Number of ways of 4-coloring a map in which there is a central circle surrounded by an annulus divided into n-1 regions. There are n regions in all.

A090860

Number of ways of 4-coloring a map in which there is a central circle surrounded by an annulus divided into n-1 regions. There are n regions in all.

Terms

    a(0) =24a(1) =72a(2) =120a(3) =264a(4) =504a(5) =1032a(6) =2040a(7) =4104a(8) =8184a(9) =16392a(10) =32760a(11) =65544a(12) =131064a(13) =262152a(14) =524280a(15) =1048584a(16) =2097144a(17) =4194312a(18) =8388600a(19) =16777224a(20) =33554424a(21) =67108872a(22) =134217720a(23) =268435464a(24) =536870904a(25) =1073741832a(26) =2147483640a(27) =4294967304

External references