Puzzle 4: The odd factors
To solve this puzzle, you need to find a clue in (virtual) Edinburgh: \(D\) is the year in which Dynamic Earth became a charitable trust. (\(D\) is a two-digit number, as written on the sign in the Gather Town space.)
You write down the integers from \(D+1\) to \(2D\) (including \(D+1\) and \(2D\)). Under each number, you write down its largest odd factor*.
What is the sum of all the odd factors you have written?
* In this puzzle, factors include 1 and the number itself.
Hint: Doing what the puzzle says may take a long time. Try doing this will some smaller values of \(D\) first and see if you can spot a shortcut.
The answer to this puzzle is a four-digit number that scores 1 points.
Read the instructions for a reminder of what these points mean.
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This puzzle hunt was written by the team behind Chalkdust, a magazine for the mathematically curious. Find out more by reading the copy of Chalkdust in your conference pack. Talk to us after solving the puzzles about how to get an article you've written printed in our next issue.