[r-t] New doubles extents

[Richard Smith]

Alexander Holroyd wrote:

> On Wed, 7 Oct 2009, Richard Smith wrote:
>
>> Something similar appears not to work in Carter because 
>> all three possible double changes appear in both 'slots', 
>> and there is no single change which contains places in 1, 
>> 3 and 5.
>
> However, the Cramboing trick does work on Carter, and 
> indeed on any in-course 60, as Robert Johnson proved a 
> while back.

Yes.  However the Tendring trick produces more elegant 
methods as it doesn't break the method's symmetry as 
the Crambo trick usually (always?) does

I do wonder, though, whether the Tendring trick can be 
generalised in any useful way to something that will work 
for all in-course 60s.

RAS