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A006074
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Number of polyaboloes (or polytans): number of different shapes that can be formed with n congruent isosceles right triangles, identifying mirror images.
(Formerly M2379)
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15
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1, 3, 4, 14, 30, 107, 318, 1116, 3743, 13240, 46476, 166358, 596638, 2158829, 7839845, 28616815, 104814161, 385269397, 1420242629, 5249877583, 19452536934, 72237904034
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OFFSET
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1,2
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COMMENTS
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Also called supertangrams: a generalization of tangrams.
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REFERENCES
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Martin Gardner, Mathematical Magic Show. Random House, NY, 1978, p. 151 (but beware errors).
T. H. O'Beirne, New Scientist, 266 (Dec 21 1961), p. 752.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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Eric Weisstein's World of Mathematics, Polyabolo
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CROSSREFS
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KEYWORD
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nonn,nice,hard,more
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AUTHOR
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EXTENSIONS
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Corrected values for a(8) and a(9), found by Aaron N. Siegel and confirmed by a Japanese puzzlist named Taro, reported by Michael Keller (Wgreview(AT)aol.com), Sep 02 2000
Modified the definition (what is a "half-square"?) and added a(13), by George Sicherman, Apr 04 2012
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STATUS
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approved
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