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Take a counter and surround it by a ring of other counters that MUST touch two others.
How many are needed? |
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Imagine surrounding this ring with more counters.
How many counters are needed?
Were you right?
What about a bigger ring?
And another? And another? |
| Or why not just lay them down according to some rule? |
What will be the 30th counter to be laid?
The 100th? The 200th? |