I would like to Generate Even and Odd Numbers below 10 based on input like if I set input as 2 it should return only Even Numbers2,4,6,8,10 if I set input 1 it should return 1,3,5,7,9 Here the code is I am unable to out of this error please help me out.
public class evenoddex {
   public integer n=10; 
   public integer a;
   public void getInput(integer x){
        a=x;
       system.debug('Your Input=='+a);
    }
   public void displayEvenOdd(){
        if(a<0){
            system.debug('Please enter postive Numbers');
        }
       else{
           if(a<n){
               for(integer i=0; i<n; i=i+2){
                   system.debug('Numbers=='+a[i]);
               }
           }
           else{
                  system.debug('Please enter Below 10');
           }
       }
    } 
}

Calling Class
-----------------------
evenoddex s=new evenoddex();
s.getInput(1);
s.displayEvenOdd();

Thanks,