# Co prime numbers

How to find a set of numbers which are coprime to each other (all numbers are pairwise co prime) ?

the numbers can be assumed to be less than a specific integers. like all numbers in the range [0,x]

• The simplest such set is the empty set. The next simplest is any single number in the range. – almagest May 13 '16 at 7:49
• How about all the prime numbers in $[1,x]$ including $1$? – bof May 13 '16 at 8:08
• {1,3,4} is also such set but 4 is not prime. (if x>=4) – Sayan Ghosh May 13 '16 at 8:21
• @SayanGhosh All you asked for was any set of such numbers. You did not ask for the largest set. – almagest May 13 '16 at 8:47
• Hasn't this question been asked before? – TheRandomGuy May 13 '16 at 11:53

Fermat numbers $F_n=2^{2^n}+1$ are pairwise coprime, see this MSE-question. This is a nice example. Of course, there are many others, for example the set of all prime numbers.