Greatest common factor with exponents of first input

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Discussion Overview

The discussion revolves around the existence of mathematical algorithms or functions, specifically G(x,y) and B(x,y), that can compute certain factors based on the prime factorization of two inputs. The focus is on how these functions would handle exponents of common prime factors and coprime factors, with implications for both theoretical and practical applications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • Some participants propose a function G(x,y) that returns a number with all and only the shared prime factors of x and y, taken to the greatest exponents that still divide x.
  • Others suggest that G(x,y) could be similar to the greatest common divisor (gcd) but with specific conditions on the exponents based on the first input.
  • One participant expresses uncertainty about the usefulness of such an algorithm and questions how it could be explained or derived.
  • Another participant emphasizes the need for a clean and simple function, suggesting that G(x,y) might be represented as gcd(x,y^x), but prefers a more precise approach.
  • There is also a proposal for a function B(x,y) that would return the divisors of x that are coprime to y, with an example provided to illustrate this idea.
  • Participants note that x will always be a factorial and y will consist of factors less than or equal to x, implying a structured relationship between the two inputs.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the existence or formulation of the proposed functions G(x,y) and B(x,y). Multiple competing views and uncertainties about their definitions and usefulness remain throughout the discussion.

Contextual Notes

Limitations include the lack of established algorithms for the proposed functions, and the discussion relies heavily on specific examples and assumptions about the nature of x and y.

DirichletHole
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ok so is there a function that exists (for all intents and purposes let's call it G(x,y) )where

x= a^2*b^4*c
y=a^4*b^2*d

G(x,y) = a^2*b^4

basically gcd, but the exponents match those of the common prime factors of the first input (x)

********
equally useful would be a function where the output would be the coprime factor(s) of the first input. ie
B(x,y) = c
 
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DirichletHole said:
ok so is there a function that exists (for all intents and purposes let's call it G(x,y) )where

x= a^2*b^4*c
y=a^4*b^2*d

G(x,y) = a^2*b^4
Actually the result would be ##a^2b^2##.

A better way to write this would be ##G(a^2b^4c, a^4b^2d) = a^2b^2##.
Is there such a function? I assume your question is, "Is there a function in some programming language that returns the GCF of its two inputs?"
I don't know, but possibly someone has written such a library function in, say, the numpy or scipy Python libraries, or some other library in some other programming language.
DirichletHole said:
basically gcd, but the exponents match those of the common prime factors of the first input (x)

********
equally useful would be a function where the output would be the coprime factor(s) of the first input. ie
B(x,y) = c
 
ok let me be more specific:

first off i am looking for a mathematical algorithm, something that could exist outside of a computer program

secondly, the equation given was purely just an example. What I need is an algorithm "G(x,y)" where, given two functions (a first function "x" and a second function "y"), G(x,y) returns a number who has all and only prime factors that are the shared prime factors of x and y, but are taken to the greatest exponents that still divide x (the first of the two functions plugged into G)

alternatively, equally useful to me would be an algorithm "B(x,y)" where, given the same two functions x and y, B(x,y) returns a number that is divisible by all and only the prime factors of x (with the exponents that they have as divisors of x) that are not shared with y.
 
DirichletHole said:
ok let me be more specific:

first off i am looking for a mathematical algorithm, something that could exist outside of a computer program

secondly, the equation given was purely just an example. What I need is an algorithm "G(x,y)" where, given two functions (a first function "x" and a second function "y"), G(x,y) returns a number who has all and only prime factors that are the shared prime factors of x and y, but are taken to the greatest exponents that still divide x (the first of the two functions plugged into G)
I'm not aware of anything like this. Are you saying that, for example, ##G(2^{10}, 2) = 2^{10}##?
I don't know how useful such an algorithm would be, but all an algorithm is, is a sequence of steps to be performed. Assuming my example follows what you're describing, how would you explain to someone how a result is achieved? That would be your algorithm.
DirichletHole said:
alternatively, equally useful to me would be an algorithm "B(x,y)" where, given the same two functions x and y, B(x,y) returns a number that is divisible by all and only the prime factors of x (with the exponents that they have as divisors of x) that are not shared with y.
 
Last edited:
Mark44 said:
I'm not aware of anything like this. Are you saying that, for example, ####G(2^{10}, 2) = 2^{10}####?
I don't know how useful such an algorithm would be, but all an algorithm is, is a sequence of steps to be performed. Assuming my example follows what you're describing, how would you explain to someone how a result is achieved? That would be your algorithm.

Yeah exactly: I'm looking for a function G(x,y) that would work exactly like the example you gave. G(2^10, 2) = 2^10.

The Algorithm would be extremely useful to me personally. I'm looking for as nice and clean and simple a function as possible. The best example i can think of so far would be G(x,y) = gcd(x,y^x), but i'd prefer something more precise, and something that would not require processing unnecessarily large numbers, as y^x would get very very large.

If such a G(x,y) can not be easily and cleanly created, a function that would be of equal use to me would be a function B(x,y) that would return the divisors of x that are coprime to y. For example B(2^10*3^5*5^8*7^3*11, 2^3*3^2*7^2) = 5^8*11
If it is at all helpful, x will always be a factorial and y will always be made up of factors less than or equal to x. So x will have prime factors that y won't have, but y will only be made up of prime factors that x also has. Also the exponents on the prime factors of y will *probably* always be less then the exponents of the prime factors of x.
 
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