There is more than one way to do this, but I like the seq builder: 
let positions = 
  seq {
    for x in 0..10 do
      for y in 0..10 do
        yield (x, y)
  }
solved how to create a seq
 
There is more than one way to do this, but I like the seq builder: 
let positions = 
  seq {
    for x in 0..10 do
      for y in 0..10 do
        yield (x, y)
  }
solved how to create a seq