1,3

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

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

M. Keller, Counting Polyforms

M. Vicher, Polyforms

Sequence in context: A229188 A345955 A091486 * A390659 A183113 A102877

Adjacent sequences: A056776 A056777 A056778 * A056780 A056781 A056782

nonn,hard,more

James Sellers, Aug 28 2000

Edited by T. D. Noe, Apr 09 2009

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

approved