MathDB
8th ibmo - mexico 1993/q1.

Source: Spanish Communities

May 7, 2006
number theory proposednumber theory

Problem Statement

A number is called capicua if when it is written in decimal notation, it can be read equal from left to right as from right to left; for example: 8,23432,64468, 23432, 6446. Let x1<x2<⋯<xi<xi+1,⋯x_1<x_2<\cdots<x_i<x_{i+1},\cdots be the sequence of all capicua numbers. For each ii define yi=xi+1−xiy_i=x_{i+1}-x_i. How many distinct primes contains the set {y1,y2,…}\{y_1,y_2, \ldots\}?
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