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

1, 1, 1, 3, 8, 35, 172, 1121, 8017, 63213

Offset: 1

Author

Don Knuth, Aug 15 2011

Keywords

• nonn
• hard
• more

Comments

The CWEB program squaregraph.w cited below relates a(n) to the number of certain partitions of {1,2,...,2*n} into n pairs.

Examples

			For n=4 the a(4)=3 cases of perimeter 8 are the two trominoes and the square tetromino.
		

References

• See A194088

Links

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

Crossrefs

A194088, A194089, A194091, A194092, A194093.

Programs

CWEB

(see Knuth link).