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1501 is a Centered Pentagonal Number

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1501 Tiny Dot Puzzle

A long time ago before calculators or computers existed, someone determined that 1501 tiny dots could be formed into a pentagon. That was a remarkable puzzle to complete! What kind of pentagon will 1501 tiny dots make?

Since 5(24)(25)/2 + 1 = 1501, it is the 25th centered pentagonal number.  Notice in the graphic below that those 1501 tiny dots can also be divided into 5 equally-sized triangles with just the center dot leftover.

Factors of 1501:

Another fact about the number 1501:

1501 is the difference of two squares in two different ways:
751² – 750² = 1501,
49² – 30² = 1501.

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