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 A220167 Number of simple squared rectangles of order n up to symmetry. 0
 3, 6, 22, 76, 247, 848, 2892, 9969, 34455, 119894, 420582, 1482874, 5254954, 18714432, 66969859, 240739417 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A squared rectangle (which may be a square) is a rectangle dissected into a finite number, two or more, of integer sized squares. If no two of these squares have the same size the squared rectangle is perfect. A squared rectangle is simple if it does not contain a smaller squared rectangle. The order of a squared rectangle is the number of constituent squares.  This sequence counts simple perfect squared rectangles and simple imperfect squared rectangles. REFERENCES See A006983 and A217156 for references and links. LINKS S. E. Anderson, Simple Perfect Squared Rectangles [Nonsquare rectangles only] S. E. Anderson, Simple Perfect Squared Squares S. E. Anderson, Simple Imperfect Squared Rectangles [Nonsquare rectangles only] S. E. Anderson, Simple Imperfect Squared Squares FORMULA a(n) = A002839(n) + A002881(n). a(n) = A006983(n) + A002962(n) + A220165(n) + A219766(n). a(n) = ((n^(-5/2))*(4^n))/(2^5*sqrt(pi)), from 'A Census of Planar Maps', William Tutte gave an asymptotic formula for the number of perfect squared rectangles where n is the number of elements in the dissection (the order). CROSSREFS Cf. A002839, A002881, A006983, A002962, A220165, A219766. Sequence in context: A208939 A209067 A220166 * A243336 A029848 A117850 Adjacent sequences:  A220164 A220165 A220166 * A220168 A220169 A220170 KEYWORD nonn,hard AUTHOR Stuart E Anderson, Dec 06 2012 EXTENSIONS a(9)-a(24) from Stuart E Anderson Dec 07 2012 STATUS approved

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Last modified August 8 23:02 EDT 2020. Contains 336300 sequences. (Running on oeis4.)