There are no 2 x 2 magic squares; they also can be defined as the only null 
  
    
      
        n
      
    
    {\displaystyle n}
   by 
  
    
      
        n
      
    
    {\displaystyle n}
   magic square set.Two also has the unique property such that,

  
    
      
        
          ∑
          
            k
            =
            0
          
          
            n
            −
            1
          
        
        
          2
          
            k
          
        
        =
        
          2
          
            n
          
        
        −
        1
      
    
    {\displaystyle \sum _{k=0}^{n-1}2^{k}=2^{n}-1}
  and also, with a not equal to zero,

  
    
      
        
          ∑
          
            k
            =
            a
          
          
            n
            −
            1
          
        
        
          2
          
            k
          
        
        =
        
          2
          
            n
          
        
        −
        
          ∑
          
            k
            =
            0
          
          
            a
            −
            1
          
        
        
          2
          
            k
          
        
        −
        1
      
    
    {\displaystyle \sum _{k=a}^{n-1}2^{k}=2^{n}-\sum _{k=0}^{a-1}2^{k}-1}
  .In any n-dimensional, euclidean space two distinct points determine a line.
For particularly invasive infections, antibiotics to cover anaerobic bacteria may be added (such as metronidazole). Treatment is typically for two weeks and often necessitates insertion of a central venous catheter or peripherally inserted central catheter. Epidemiology
The current incidence in the United States is somewhere around 0.5% per year; overall, the incidence rate for developed world falls between 0.2 and 0.7%. In developing countries, the incidence of omphalitis varies from 2 to 7 for 100 live births. There does not appear to be any racial or ethnic predilection. Like many bacterial infections, omphalitis is more common in those patients who have a weakened or deficient immune system or who are hospitalized and subject to invasive procedures. Therefore, infants who are premature, sick with other infections such as blood infection (sepsis) or pneumonia, or who have immune deficiencies are at greater risk. Infants with normal immune systems are at risk if they have had a prolonged birth, birth complicated by infection of the placenta (chorioamnionitis), or have had umbilical catheters. References


== External links ==