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%I A367435 #7 Nov 18 2023 13:21:27
%S A367435 0,0,1,8,45,254,1258,6181,28062,125714,550402,2394654,10326665
%N A367435 Let PG(n) be the graph with one node for each free n-celled polyomino and edges between nodes corresponding to polyominoes that can be obtained from each other by moving one cell, where the intermediate (the set of cells remaining when the cell to be moved is detached) is required to be a (connected) polyomino. a(n) is the number of edges in PG(n).
%C A367435 Equivalently, there is an edge between two nodes if the corresponding n-celled polyominoes can be obtained from the same (n-1)-celled polyomino by adding one cell.
%C A367435 In the n-omino graph defined in A098891, the intermediate is not required to be a polyomino, so PG(n) is a spanning subgraph of that graph. For n = 5, for example, there is an edge between the V and W pentominoes in the graph in A098891, but not in PG(5).
%H A367435 <a href="/index/Pol#polyominoes">Index entries for sequences related to polyominoes</a>.
%F A367435 a(n) <= A098891(n).
%Y A367435 Half the row sums of A367439.
%Y A367435 Cf. A000105, A098891, A367436, A367437, A367438, A367440, A367441, A367443.
%K A367435 nonn,more
%O A367435 1,4
%A A367435 _Pontus von Brömssen_, Nov 18 2023

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