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 A119611 Number of free polyominoes in {4,5} tessellation of the hyperbolic plane. 5
 1, 1, 1, 2, 5, 16, 55, 224, 978, 4507, 21430, 104423, 517897, 2606185, 13272978 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS Code Golf Stack Exchange Impress Donald Knuth by counting polyominoes on the hyperbolic plane Don Hatch, Hyperbolic Planar Tesselations: {4,5}. Eric Weisstein's World of Mathematics, Polyomino. Wikipedia, Order-5 square tiling EXAMPLE For n = 0,1,2,3 the polyominoes in the {4,5} tessellation of the hyperbolic plane are essentially same as the ordinary polyominoes in the plane (A000105), with redefinition of "straight line" and angular deficiency at a vertex. For n = 4, the square tetromino does not exist. In its place is the cut-square, a pentagonal pentomino with one cell removed. For n = 5, see links section. PROG Several working programs are available via the Code Golf link. CROSSREFS Cf. A000105. Sequence in context: A333233 A019988 A137732 * A057973 A102461 A176332 Adjacent sequences:  A119608 A119609 A119610 * A119612 A119613 A119614 KEYWORD nonn,more AUTHOR Jonathan Vos Post, Jun 04 2006 EXTENSIONS a(5) corrected by Don Knuth a(6) corrected by Christian Sievers a(7)-a(10) from Christian Sievers a(11)-a(14) from Ed Wynn, Feb 14 2021 STATUS approved

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Last modified August 5 15:41 EDT 2021. Contains 346477 sequences. (Running on oeis4.)