ZeroOneString←{
⍝ ←: ⍵th number in the series defined as follows
⍝ (S 0) = '' ⋄ (S 1) = '0' ⋄ (S ⍵) = (S ⍵-1),'0',~⌽S ⍵-1
     S←{
         ⍵=0:⍬
         p←∇ ⍵-1
         p,0,~⌽p
     }
     (⍕S ⍵)~' '
 }