A194089 The number of labeled biconnected squaregraphs that contain n squares

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

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 A361844 A047891

Adjacent sequences: A194086 A194087 A194088 * A194090 A194091 A194092

Keyword

nonn,hard,more

Author

Don Knuth, Aug 15 2011

Status

approved