

A194089


The number of labeled biconnected squaregraphs that contain n squares


5




OFFSET

1,2


REFERENCES

see A194088


LINKS

Table of n, a(n) for n=1..9.
Don Knuth, squaregraph.w (CWEB program).


EXAMPLE

A biconnected squaregraph is "labeled" if one of the edges on its periphery is given an orientation. The a(2)=3 examples with n=2 are the domino together with two possible ways to orient one of the edges on its "long" side, and one way to orient an edge on the short side. If a squaregraph has m automorphisms and perimeter 2p, the number of different ways to label it is 4p/m.


PROG

(CWEB) (see Knuth link).


CROSSREFS

cf. A194088, A194090, A194091, A194092, A194093.
Sequence in context: A165310 A133158 A328295 * A178807 A047891 A166991
Adjacent sequences: A194086 A194087 A194088 * A194090 A194091 A194092


KEYWORD

nonn,hard,more


AUTHOR

Don Knuth, Aug 15 2011


STATUS

approved



