A194089 The number of labeled biconnected squaregraphs that contain n squares.

1, 3, 12, 57, 295, 1615, 9190, 53811, 322078

Offset: 1

Author

Don Knuth, Aug 15 2011

Keywords

• nonn
• hard
• more

Examples

			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.
		

References

• see A194088

Links

• Don Knuth, squaregraph.w (CWEB program).

Crossrefs

cf. A194088, A194090, A194091, A194092, A194093.

Programs

CWEB

(see Knuth link).