Number of staircase polygons of area n with one (staircase polygon) hole on square lattice (not allowing rotations).

A057414

Number of staircase polygons of area n with one (staircase polygon) hole on square lattice (not allowing rotations).

Terms

    a(0) =1a(1) =4a(2) =18a(3) =62a(4) =205a(5) =624a(6) =1841a(7) =5214a(8) =14448a(9) =39118a(10) =104281a(11) =273900a(12) =711416a(13) =1828950a(14) =4663203a(15) =11801056a(16) =29677044a(17) =74209404a(18) =184655403a(19) =457446252a(20) =1128794669a(21) =2775534900a(22) =6802886782a(23) =16625602146a(24) =40524317635a(25) =98537954476a(26) =239072427508a(27) =578853345494

External references