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%I #11 Dec 05 2014 02:43:36
%S 1,1,1,3,4,12,21,56,111,261,462,1431,1875,4696,9410,20099,24034,77884,
%T 79925,266786,358096,658594,796571,3227163,2980476,6268017,10167660,
%U 24321735,21477012,85964698
%N Number of polyiamonds with n cells that tile the plane by 180-degree rotation (Conway criterion).
%D Branko Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987, Section 9.4.
%H Joseph Myers, <a href="http://www.polyomino.org.uk/mathematics/polyform-tiling/">Polyiamond tiling</a>
%Y Cf. A071332, A075216, A075217, A075218, A075219, A075221, A075222, A075223, A075224, A075202, A075211.
%K hard,nonn
%O 1,4
%A _Joseph Myers_, Sep 08 2002
%E More terms from _Joseph Myers_, Nov 11 2003
%E a(29) and a(30) from _Joseph Myers_, Nov 21 2010