I have forgotten the number of the combination of the lock on my briefcase. I did have a method for remembering it...
Sam displays cans in 3 triangular stacks. With the same number he could make one large triangular stack or stack them all in a square based pyramid. How many cans are there how were they arranged?
Here is a collection of puzzles about Sam's shop sent in by club members. Perhaps you can make up more puzzles, find formulas or find general methods.
Keep a record of your results.
How might square roots help when determining whether or not a number is a triangle number?