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Radioactive Coins (Posted on 2006-10-17) Difficulty: 5 of 5
You have N coins, 2 of which are radioactive. You have a radioactivity detector which can test any subset of the coins at a time, and return the number of radioactive coins in the group (i.e. it returns 0, 1 or 2). You have to find the radioactive coins, using not more than 10 tests. What is the largest N for which this is possible?

No Solution Yet Submitted by David Shin    
Rating: 4.5000 (6 votes)

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re(3): Fibonacci Connection.....placed | Comment 17 of 18 |
(In reply to re(2): Fibonacci Connection.....placed by Ady TZIDON)

Nice find.  But the two series diverge on the next term: the next term of OEIS A164509 is 331 and the next term of S(n)=floor[sqrt(3)*S(n-1)] is floor[sqrt(3)*193] = 334.  We'll have to see if someone can compute S(11) to know which one.  So far we only know S(8) for sure.
  Posted by Brian Smith on 2016-02-15 23:10:12

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