[obm-l] Contagem e bijeção

["Domingos Jr." <dopikas@xxxxxxxxxx>]

Let s(n) be the number of sequences of elements from the set {1,...,n} for
which each term is at least twice the preceding one, and u(n) the number of
such sequences in which each term is greater than the sum of its
predecessors. It is known that u(n) - u(n-1) = s(n)/2. Problem: Find a
bijective proof.

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