functions that f(n) is not O(g(n)) and g(n) is not O(f(n))

Question

Are there any functions such as f(n) and g(n) that both;

f(n) != O(g(n)) and
g(n) != O(f(n)). 

Are there any functions that fulfills the requir

Answer 1

 f(n)=n and g(n)=n^(1 + sin(x)). 

f(n) is not O(g(n)) and g(n) is not O(f(n)).

Refer http://c2.com/cgi/wiki?BigOh