[r-t] Gangnam (or whatever) etc.

[Richard Smith]

Simon Gay wrote:

> Consider the rows of the form 56xxx1 and 65xxx1.
>
> There are 12 such rows, and they occur 4 per lead, with lead heads of the 
> form 15xxx6 or 16xxx5.

They can appear in lots of non-fixed-treble leads too. 
That was my point.  Nevertheless, the proof for the case of 
fixed-treble extents is interesting, if not particularly 
surprising, so thanks for putting it down on paper (well, 
screen).

RAS