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%I #9 Dec 13 2025 05:25:18
%S 0,0,0,0,0,0,1,7,63,458,3209,21160,135308,843204,5165292
%N a(n) is the number of concave n-celled polyominoes in the {4,5} tessellation of the hyperbolic plane.
%C Define a {4,5} polyomino as being concave if one of the "straight" lines that connects the centers of adjacent squares in the lattice enters the polyomino more than once.
%C This sequence was calculated in the context of a project in collaboration with Érika Roldán, and Rosemberg Toalá-Enríquez.
%Y Cf. A119611.
%K nonn,more
%O 1,8
%A _John Mason_, Nov 02 2025