Difference between revisions of "1990 OIM Problems/Problem 1"

(Created page with "== Problem == Let <math>f</math> be a function defined in the set of integers greater or equal to zero such that: (i) If <math>n=2^j-1</math>, for all <math>n=0, 1, 2, \cdots...")
 
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<cmath>f(n)+n=2^k-1</cmath>
 
<cmath>f(n)+n=2^k-1</cmath>
  
b. Calculate <math>f(2^1990)</math>.
+
b. Calculate <math>f(2^{1990})</math>.
  
 
~translated into English by Tomas Diaz. ~orders@tomasdiaz.com
 
~translated into English by Tomas Diaz. ~orders@tomasdiaz.com

Revision as of 23:51, 22 December 2023

Problem

Let $f$ be a function defined in the set of integers greater or equal to zero such that:

(i) If $n=2^j-1$, for all $n=0, 1, 2, \cdots,$ then $f(n)=0$

(ii) If $n \ne 2^j-1$, for all $n=0, 1, 2, \cdots,$ then $f(n+1)=f(n)-1$

a. Prove that for all integer $n$, greater or equal to zero, there exist an integer $k$ grater than zero such that \[f(n)+n=2^k-1\]

b. Calculate $f(2^{1990})$.

~translated into English by Tomas Diaz. ~orders@tomasdiaz.com

Solution

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See also

https://www.oma.org.ar/enunciados/ibe5.htm