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%I #19 Nov 13 2023 19:02:07
%S 1,1,2,6,18,72,318,1601,8417
%N The number of biconnected squaregraphs that contain n squares.
%D V. Chepoi, F. Dragan, Y. Vaxès, Center and diameter problem in planar quadrangulations and triangulations, SODA 13 (2002), 346--355.
%D H.-J. Bandelt, V.Chepoi, and D. Eppstein, Combinatorics and geometry of finite and infinite squaregraphs, SIAM Journal on Discrete Mathematics 24 (2010), 1399--1440.
%H Don Knuth, <a href="https://www-cs-faculty.stanford.edu/~knuth/programs/squaregraph.w">squaregraph.w</a> (CWEB program).
%e For n=5 the a(5)=18 solutions are the 12 pentominoes, plus the "5-cogwheel", plus five others obtained by "tearing" the P-pentomino or the 5-cogwheel apart at one edge.
%o (CWEB) @ See Knuth link.
%Y Cf. A194089, A194090, A194091, A194092, A194093.
%K nonn,more
%O 1,3
%A _Don Knuth_, Aug 15 2011