My first Ruby program!

This is my first Ruby program!

N = 13
def un( el, en )
  [1, en-1].include?(el%en)?re=1:re=" "; return re
end

(N-1).times do a
  (1...N-1).to_a.each{b print un((b+1)*(a+1),N), " "}
  print "\n"
end

A little obscure, isn't it?
The output is ( as desired ):

1                     1
          1 1    
      1         1
    1             1
        1     1  
  1                 1
  1                 1
        1     1  
    1             1
      1         1
          1 1    
1                     1

The same program in Scala can be written in this way:

object something {
  val un = ( el:Double, en:Double ) =>
    if( Array(1,en-1).contains( el%en) ) "1 " else "  "
                                  
  def main(args : Array[String]) : Unit = {
    val N = 23
    for(i <- 1 to N-1){ new Array(N-1)
     .indices.foreach(el => print( un((el+1)*(i),N) ))
      println()
    }
  }
}

and the output with N=23 is:
1                                         1
                    1 1              
              1             1        
          1                     1    
                1         1          
      1                             1
                  1     1            
    1                                 1
        1                         1  
            1                 1      
  1                                     1
  1                                     1
            1                 1      
        1                         1  
    1                                 1
                  1     1            
      1                             1
                1         1          
          1                     1    
              1             1        
                    1 1              
1                                         1