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%I #8 Mar 31 2012 10:22:49
%S 1,1,1,3,8,35,172,1121,8017,63213
%N The number of biconnected squaregraphs of perimeter 2*n.
%C The CWEB program squaregraph.w cited below relates a(n) to the number of certain partitions of {1,2,...,2*n} into n pairs.
%D See A194088
%H Don Knuth, <a href="http://www-cs-faculty.stanford.edu/~knuth/programs/squaregraph.w">squaregraph.w</a> (CWEB program).
%e For n=4 the a(4)=3 cases of perimeter 8 are the two trominoes and the square tetromino.
%o (CWEB) (see Knuth link).
%Y A194088, A194089, A194091, A194092, A194093.
%K nonn,hard,more
%O 1,4
%A _Don Knuth_, Aug 15 2011
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