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?

(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.