Calculating The Nth Rational Number

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Discussion Overview

The discussion revolves around the mapping of natural numbers to rational numbers, specifically exploring the possibility of defining a "distance" between consecutive terms in this mapping and calculating the nth term of such a progression. The scope includes theoretical aspects of number theory and mathematical reasoning.

Discussion Character

  • Exploratory
  • Mathematical reasoning

Main Points Raised

  • One participant suggests that if a specific method for mapping natural numbers to rationals is defined, it may be possible to specify a "distance" between consecutive terms and calculate the nth term using this distance function.
  • Another participant questions the clarity of the initial question, asking for clarification on terms like "two consecutive terms," "nth term," and "progression."
  • A later reply reiterates the importance of defining a function that maps natural numbers to rationals, indicating that if such a function exists, one could determine the difference between consecutive terms, but the existence of a reasonable formula depends on the specific mapping.
  • One participant references an external algorithm for calculating the nth term in a specific sequence, indicating that such methods exist.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and clarity regarding the initial question, and while some agree on the potential for mapping and calculating terms, the discussion remains unresolved regarding the specifics of such mappings and the existence of reasonable formulas.

Contextual Notes

The discussion highlights the need for clear definitions and assumptions regarding the mapping of natural numbers to rationals, as well as the conditions under which reasonable formulas may exist.

moyo
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Hallo

If we specify a particular method for mapping the natural numbers to the rationals, could we also specify a "distance" between two consecutive terms in some general way. Also are we able to calculate the nth term in such a progression perhaps incorporating this distance function somehow within its expression.
 
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Your question is not very clear. What are you referring to when you say "two consecutive terms", "nth term" and "progression"?
 
moyo said:
Hallo

If we specify a particular method for mapping the natural numbers to the rationals, could we also specify a "distance" between two consecutive terms in some general way. Also are we able to calculate the nth term in such a progression perhaps incorporating this distance function somehow within its expression.

If "we specify a particular method for mapping the natural numbers to the rationals" is the key. If we have some function \{a_n\} such that to every natural number n, we have a rational number a_n and every rational number is on that list, then, for any n we could determine a_{n+1}- a_n. Whether there would be any reasonable formula for that function of n depends on the mapping. And asking whether "we able to calculate the nth term in such a progression" is asking whether there exist a reasonable function describing that progression.

Since the rational numbers are countable, such progressions exist but whether or not there exist reasonable formulas for calculating them depends on the progression.
 

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