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Sunday Afternoon Maths LVII

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 Posted on 2016-11-27 

Square Factorials

Source: Woody at Maths Jam
Multiply together the first 100 factorials:
$$1!\times2!\times3!\times...\times100!$$
Find a number, \(n\), such that dividing this product by \(n!\) produces a square number.

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Largest Odd Factors

Pick a number. Call it \(n\). Write down all the numbers from \(n+1\) to \(2n\) (inclusive). For example, if you picked 7, you would write:
$$8,9,10,11,12,13,14$$
Below each number, write down its largest odd factor. Add these factors up. What is the result? Why?

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If you enjoyed these puzzles, check out Sunday Afternoon Maths LXI,
puzzles about arrows, or a random puzzle.
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