36 Rhombi in an Octadecagon

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Two Versions of Mandalas Centered on Regular Octadecagons

18

18b

Twice Nine Is Eighteen

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9

Countdown

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Countdown

Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school. Eighteen more days of school.

Tessellation Using Regular Octadecagons and Triconcave, Equilateral Hexagons

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Tessellation Using Regular Octadecagons and Triconcave Equilateral Hexagons

An Octadecagon, with Its Circumscribed Circle, and the Lines Containing All of Its Sides and Diagonals

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An Octadecagon, with Its Circumscribed Circle, and the Lines Containing All of Its Sides and Diagonals

Nine Times Two Is Eighteen

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Seven Times Two Is Fourteen

Mandala Based on the Number 18

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Mandala Based on the Number 18