login
A194088
The number of biconnected squaregraphs that contain n squares.
5
1, 1, 2, 6, 18, 72, 318, 1601, 8417
OFFSET
1,3
REFERENCES
V. Chepoi, F. Dragan, Y. Vaxès, Center and diameter problem in planar quadrangulations and triangulations, SODA 13 (2002), 346--355.
H.-J. Bandelt, V.Chepoi, and D. Eppstein, Combinatorics and geometry of finite and infinite squaregraphs, SIAM Journal on Discrete Mathematics 24 (2010), 1399--1440.
LINKS
Don Knuth, squaregraph.w (CWEB program).
EXAMPLE
For n=5 the a(5)=18 solutions are the 12 pentominoes, plus the "5-cogwheel", plus five others obtained by "tearing" the P-pentomino or the 5-cogwheel apart at one edge.
PROG
(CWEB) @ See Knuth link.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Don Knuth, Aug 15 2011
STATUS
approved