Code:
alias make.bin {
  var %bin = $+($rand(0,1),$rand(0,1)) 
  var %size = 30
  var %i = 3
  while (%i <= %size) {
    var %new = $rand(0,1)
    if ($invalid.binary($+(%bin,%new))) {
      var %failsize = $v1 
      var %new = $iif(%new,0,1)
      if ($invalid.binary($+(%bin,%new))) {
        if ($v1 > %failsize) { var %failsize = $v1 }
        dec %i %failsize
        var %bin = $left($+(%bin,%new),$calc(-1 * %failsize))
        var %new
      }
    }
    var %bin = $+(%bin,%new)
    inc %i
  }
  return %bin
}
alias -l invalid.binary {
  var %max = $int($calc($len($1) / 3))
  var %c = 1
  while (%c <= %max) {
    if (($right($1,%c) == $left($right($1,$calc(%c * 2)),%c)) && ($right($1,%c) == $left($right($1,$calc(%c * 3)),%c))) { return %c }
    inc %c
  }
}


usage //echo $make.bin

* code was tested to work
* but i dont garrentee it works as specified, i couldnt be shagged writting a checking script, but since the invalid.binary routine should check it at 30 chars anyway I would assume its valid results.

Someone might like to validate it if they can be shagged.