The series 
 for a monotonic nonincreasing 
 is convergent if
and divergent if
 
	    
	
    
The series 
 for a monotonic nonincreasing 
 is convergent if
and divergent if
Weisstein, Eric W. "Ermakoff's Test." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/ErmakoffsTest.html