%I A006746 M1573
%S A006746 0,0,0,1,2,6,9,23,38,90,147,341,564,1294,2148,4896,8195,18612,31349,70983,
               120357,
%T A006746 271921,463712,1045559,1792582,4034832,6950579,15619507
%N A006746 Number of axially symmetric polyominoes with n cells.
%C A006746 Number of polyominoes with n cells and exactly one line of reflection 
               symmetry, where that one line is parallel to the grid. - Joshua Zucker, 
               Mar 08 2008
%D A006746 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A006746 D. H. Redelmeier, Counting polyominoes: yet another attack, Discrete 
               Math., 36 (1981), 191-203.
%H A006746 Tomas Oliveira e Silva, <a href="http://www.ieeta.pt/~tos/animals.html">
               Enumeration of polyominoes</a>
%H A006746 D. H. Redelmeier, <a href="a056877.png">Table 3</a> of Counting polyominoes...
%Y A006746 Cf. A000105, A001168, A006746, A056877, A006748, A056878, A006747, A006749, 
               A030227.
%Y A006746 Sequences classifying polyominoes by symmetry group: A000105, A006746, 
               A006747, A006748, A006749, A056877, A056878, A142886, A144553, A144554.
%Y A006746 Sequence in context: A127931 A077237 A056879 this_sequence A121624 A103019 
               A101823
%Y A006746 Adjacent sequences: A006743 A006744 A006745 this_sequence A006747 A006748 
               A006749
%K A006746 nonn
%O A006746 1,5
%A A006746 N. J. A. Sloane (njas(AT)research.att.com).
%E A006746 Extended to n=28 by Tomas Oliveira e Silva.