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A194090 The number of biconnected squaregraphs of perimeter 2*n. 5

%I

%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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Last modified September 19 19:41 EDT 2021. Contains 347564 sequences. (Running on oeis4.)