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A056779 Number of poly-IH73-tiles (holes allowed) with n cells. 1
1, 1, 3, 7, 21, 60, 208, 704, 2542, 9192, 34053, 126771, 476849, 1802367, 6851960, 26152629 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Originally from Vicher's table, which lists this as "Puzzle 3".

Isohedral tiling IH73 (see Figure 6.2.4 of Grünbaum and Shephard) is obtained from the regular square tiling by replacing the edges of each square by symmetric curves bulging alternately inwards and outwards, so that each modified square now has a rotation of order two and reflections in horizontal and vertical axes as symmetries but no longer has rotations of order four or diagonal reflections as symmetries. - Joseph Myers, Oct 08 2011

REFERENCES

Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987, Sections 6.2 and 9.4.

LINKS

Table of n, a(n) for n=1..16.

M. Keller, Counting Polyforms

M. Vicher, Polyforms

CROSSREFS

Sequence in context: A035080 A229188 A091486 * A183113 A102877 A122983

Adjacent sequences:  A056776 A056777 A056778 * A056780 A056781 A056782

KEYWORD

nonn,hard

AUTHOR

James A. Sellers, Aug 28 2000

EXTENSIONS

Edited by T. D. Noe, Apr 09 2009

Edited and a(11)-a(16) by Joseph Myers, Oct 08 2011

STATUS

approved

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Last modified October 18 07:58 EDT 2018. Contains 316307 sequences. (Running on oeis4.)