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 A006074 Number of polyaboloes (or polytans): number of different shapes that can be formed with n congruent isosceles right triangles, identifying mirror images. (Formerly M2379) 5
 1, 3, 4, 14, 30, 107, 318, 1116, 3743, 13240, 46476, 166358, 596638, 2158829, 7839845 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also called supertangrams: a generalization of tangrams. REFERENCES 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). LINKS Ed Pegg, Jr., Illustrations of polyforms Andrew Clarke, Polyaboloes Andrew Clarke, Illustration of initial terms Michael Keller, Counting Polyforms Henri Picciotto, Geometric Puzzles Miroslav Vicher, Polyforms Eric Weisstein's World of Mathematics, Polyabolo. CROSSREFS Cf. A151519 (distinguishing mirror images), A245676 (number of convex polyaboloes). - George Sicherman, Nov 25 2017 Sequence in context: A080878 A110565 A057433 * A081714 A117718 A268700 Adjacent sequences:  A006071 A006072 A006073 * A006075 A006076 A006077 KEYWORD nonn,nice,hard,more AUTHOR EXTENSIONS Corrected values for a(8) and a(9), found by Aaron Siegel and confirmed by a Japanese puzzlist named Taro, reported by Michael Keller (Wgreview(AT)aol.com), Sep 02 2000 One more term from Vladeta Jovovic, Aug 11 2007 Link updated by William Rex Marshall, Dec 16 2009 Modified the definition (what is a "half-square"?) and added a(13), by George Sicherman, Apr 04 2012 a(14) from Juris Cernenoks, Sep 06 2012 a(15) from George Sicherman, Aug 02 2013 STATUS approved

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Last modified November 20 02:57 EST 2018. Contains 317371 sequences. (Running on oeis4.)