"first"

1 to: 6 do: [:i |
      1 to: i do: [:j |
            Transcript show: (i odd ifTrue: j ifFalse: i-j+1);
        show: (i=j ifTrue: '' ifFalse: $-)].
      Transcript cr].

"and second, in one line"

1 to:6 do:[:i|1 to:i do:[:j|Transcript show:(i odd ifTrue:j ifFalse:i-j+1);show:(i=j ifTrue:''ifFalse:$-)].Transcript cr].