module lcyl(size, depth){
  translate([size/2,depth/2,size/2])
    rotate([90,0,0])
      cylinder(h = depth, d = size, center = true, $fn = 32);
}

module binary(n, size, depth = size, sep = size/2){
  cube([sep,depth,size]);
  translate([0,0,-size/4])
    lcyl(size = sep, depth = depth);
  translate([0,0,3*size/4])  
    lcyl(size = sep, depth = depth);
  translate([2*sep,0,0])  
    binary_rec(n = n, size = size, depth = depth, sep = sep);  
}

module binary_rec(n, size, depth, sep){
  if(n != 0){
    if(n % 2 == 0){
      translate([size+sep,0,0])
        binary_rec(n = n/2, size = size, depth = depth, sep = sep);
    }
    else{
      lcyl(size = size, depth = depth);
      translate([size+sep,0,0])
        binary_rec(n = (n-1)/2, size = size, depth = depth, sep = sep);
    }
  }
} 

binary(n = 23, size = 2, depth = 2, sep = 1);