Difference between revisions of "1993 OIM Problems/Problem 1"

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== Problem ==
 
== Problem ==
A natural number is a palindrome if when written in decimal notation, it can be read equally from left to right and from right to left, for example: 8, 23432, 6446.
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A natural number is a palindrome if, when written in decimal notation, it is the same when written from left to right and from right to left; for example: 8, 23432, 6446.
  
Let <math>x_1<x_2 < \cdots < x_i<x_{i+1}< \cdots</math> all be palindrome numbers. For each <math>i</math> let <math>y_{i+1} = x_{i+1}-x_i</math>.
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Let <math>x_1<x_2 < \cdots < x_i<x_{i+1}< \cdots</math> be all the palindromes. For each <math>i</math>, let <math>y_{i+1} = x_{i+1}-x_i</math>.
  
How many different prime numbers does the set <math>{y_1,y_2,y_3,\cdots }</math> have?
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How many different prime numbers does the set <math>{y_1,y_2,y_3,\cdots }</math> contain?
  
 
~translated into English by Tomas Diaz. ~orders@tomasdiaz.com
 
~translated into English by Tomas Diaz. ~orders@tomasdiaz.com
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~ Edits by [https://artofproblemsolving.com/wiki/index.php/User:Eevee9406 eevee9406]
  
 
== Solution ==
 
== Solution ==

Revision as of 18:16, 22 March 2025

Problem

A natural number is a palindrome if, when written in decimal notation, it is the same when written from left to right and from right to left; for example: 8, 23432, 6446.

Let $x_1<x_2 < \cdots < x_i<x_{i+1}< \cdots$ be all the palindromes. For each $i$, let $y_{i+1} = x_{i+1}-x_i$.

How many different prime numbers does the set ${y_1,y_2,y_3,\cdots }$ contain?

~translated into English by Tomas Diaz. ~orders@tomasdiaz.com ~ Edits by eevee9406

Solution

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See also

https://www.oma.org.ar/enunciados/ibe8.htm