MathDB
9th ibmo - brazil 1994/q6.

Source: Spanish Communities

May 7, 2006
inductionalgebra unsolvedalgebra

Problem Statement

Show that every natural number n21  000  000n\leq2^{1\;000\;000} can be obtained first with 1 doing less than 1  100  0001\;100\;000 sums; more precisely, there is a finite sequence of natural numbers x_0,\ x_1,\dots,\ x_k\mbox{ with }k\leq1\;100\;000,\ x_0=1,\ x_k=n such that for all i=1, 2,, ki=1,\ 2,\dots,\ k there exist r, sr,\ s with 0rs<i0\leq{r}\leq{s}<i such that xi=xr+xsx_i=x_r+x_s.