# [✓] Get the number of Integers coprime to X less than Y?

Posted 9 months ago
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 Wolfram understands Coprime/relatively prime and will output a list of integers if you input something like: integers | coprime to 35 But it doesn't seem to let you do anything else with the coprime function. I want to be able to do things like count the number of integers coprime to a number X less than Y, or in a range [k, k+-Y]I've tried things like this: integers | less than 20 | coprime to 35 Intersection[ {integers less than 20}, {integers | coprime to 35}] But nothing seems to work. If anyone can give me some help that would be great.Thanks in advance.
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Posted 9 months ago
 Hi,this (pure) function tests whether a particular number is coprime to 35 and smaller than 20. CoprimeQ[35, #] && # < 20 & You can apply this to all function in a certain range: Select[Range[-100, 100], CoprimeQ[35, #] && # < 20 &] Of course this is not quite necessary, because technically we can add the range restriction in the first place to the input: Select[Range[-100, 19], CoprimeQ[35, #] &] gives the same as above.Cheers,Marco