

A194090


The number of biconnected squaregraphs of perimeter 2*n.


5




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: A304726 A226679 A216541 * A294385 A020099 A182392
Adjacent sequences: A194087 A194088 A194089 * A194091 A194092 A194093


KEYWORD

nonn,hard,more


AUTHOR

Don Knuth, Aug 15 2011


STATUS

approved



