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

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

Offset

1,4

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.

References

See A194088

Links

Table of n, a(n) for n=1..10.

Don Knuth, squaregraph.w (CWEB program).

Example

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

Prog

(CWEB) (see Knuth link).

Crossrefs

A194088, A194089, A194091, A194092, A194093.

Sequence in context: A226679 A216541 A347896 * A294385 A020099 A182392

Adjacent sequences: A194087 A194088 A194089 * A194091 A194092 A194093

Keyword

nonn,hard,more

Author

Don Knuth, Aug 15 2011

Status

approved