 mersenneforum.org > Math least common multiple of numbers of the form a^x-1
 Register FAQ Search Today's Posts Mark Forums Read 2004-04-17, 10:42 #1 juergen   Mar 2004 2910 Posts least common multiple of numbers of the form a^x-1 Hello, what is the form of the least common multiple of numbers of the form v^(a*b*c) - 1, v^(a*b*d) - 1, v^(a*c*d) - 1 and v^(b*c*d) - 1 ? I know that it is not just the product of these numbers. Sorry unfortunately I can't use math symbols here. As I wrote this article I recognized that without mathematical symbols like the sum sing (sigma) it looks pretty much complicated. But I guess my question it is not that complicated in reality. So If you try to understand the following (which may be not necessary to answer the question anyway) then I suggest you to write it down on paper in the mathematical form using the sum sign. Sorry for this inconvenience. Why do they have dozens of different smiley simbols here, but no mathematical symbols in a forum which is about math? I use Si(a,b,f(i)) for the sum sign with the variable i running from a to b. So Si(a,b,f(i)) would build the sum of all the results of f(i) for all the values of i which are between a and b => so Si(....) is just my textual representation of the Singma-Sign :o). Using this notation for sigma the least common multiple [v^(a*b*c) - 1; v^(a*b*d) - 1; v^(a*c*d) - 1; v^(b*c*d) - 1] could be reduced by using polinom division (v^(ab)-1 is a factor of (v^(abc) - 1) as well als of (v^(abd) - 1) to the following: [v^(a*b*c) - 1; Si(0 ,d-1, v^(i*a*b)); Si(0 ,d-1, v^(i*a*c)); Si(0 ,d-1, v^(i*b*c))] but it seems that also Si(0 ,d-1, v^(i*a*b)) and Si(0 ,d-1, v^(i*a*c)) and Si(0 ,d-1, v^(i*b*c)) have common divisors. Is there a formula for this common divisor? Thank you very much in advance Juergen Bullinger Last fiddled with by juergen on 2004-04-17 at 10:45   2004-04-17, 10:53   #2
cyrix

Jul 2003
Thuringia; Germany

2·29 Posts Quote:
 Originally Posted by juergen [...] Sorry unfortunately I can't use math symbols here. As I wrote this article I recognized that without mathematical symbols like the sum sing (sigma) it looks pretty much complicated. [...] Juergen Bullinger
You could use LATeX-Code, or attach a file, were you could use the symbols you need.

Cyrix   2004-04-17, 12:19   #3
juergen

Mar 2004

29 Posts Quote:
 Originally Posted by cyrix You could use LATeX-Code, or attach a file, were you could use the symbols you need. Cyrix
Thank you for your suggestion. I don't know how to add files here, so I put a pdf file on a web server you can download it on

informatik.gmxhome.de/lcm.pdf

Kind regards

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