O kockách a pyramídach

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• [hádanka] Matematika ukladania plechoviek
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• Centered hexagonal number

  The sum of the first n centered hexagonal numbers is n³. That is, centered hexagonal pyramidal numbers and cubes are the same numbers, but they represent different shapes. Viewed from the opposite perspective, centered hexagonal numbers are differences of two consecutive cubes, so that the centered hexagonal numbers are the gnomon of the cubes.