[r-t] Challenge to produce new method - Double Helix Royal

[Alexander Holroyd]

> My challenge for people now is to come up with a royal differential (or 
> even a long list of possibilities) matching these constraints:

As a first stab at this, I offer what I hope is a list of all possible 
extent-yielding double 3/7 differentials using only the place notations -, 
50 and 16.  These don't satisfy all Philip's criteria, in particular with 
regard to the allowed pieces of work.  Also the music is likely to be 
dire.  However, it is a proof of concept.  The place notation given is for 
the first quarter-lead.  A - at the quarter lead needs to be added, as do 
half-lead and lead-end changes (in many cases 5 and 6 respectively work 
for these).

Ander

-6-5-56-5-6-656-6565656-5656565-5656-65-5-5-5-6-5-6-56565-5
-6-5-56-5-6-656-6565656-5656565-5656-6565-5-5-6-5-6-56565-5
-6-5-65-5-5-5-6-5-6-5-6-5-6-6-6-65-5-5656-65-5-56565-56-5-6
-6-5-65-5-5-5-6-5-6-5-6-5-6-6-6565-5-5656-65-5-56565-56-5-6
-6-5-65-5-6-56-6565-5-56-6-5-5-6-5-5-5-6-5-6-6-56565-56-5-6
-6-5-65-5-6-56-6565-5-5656-5-5-6-5-5-5-6-5-6-6-56565-56-5-6
-6-5-65-565-65-5-5-5-56-6-6565-56-56-6-5-6-5-65-5-5656-6565
-6-5-65-565-65-5-5-5656-6-6565-56-56-6-5-6-5-65-5-5656-6565
-6-56-5-6-65-5656-656565656-656565656-6-5-56565-6-6565-5656
-6-56-5-6565-5656-656565656-656565656-6-5-56565-6-6565-5656
-6-565-6565-5-65-5656565-6565656-6565-56-6-56-5-6-5-6-5-656
-6-565-6565-5-65-5656565-6565656-6565-5656-56-5-6-5-6-5-656
-6-565-6565-56565-565-6-65-5-656-565-5-656-65-656-5-6-5-5-6
-6-565-6565-56565-565-6-65-56-656-5-6-5-5-6565656-56565-6-6
-6-565-6565-56565-565-6-65-5656-5-656565656-6-56565-6565656
-6-565-6565-56565-565-6-65-5656-56-65656-5-656565656-565656
-6-565-6565-56565-565-6565-5-656-565-5-656-65-656-5-6-5-5-6
-6-565-6565-56565-565-6565-56-656-5-6-5-5-6565656-56565-6-6
-6-565-6565-56565-565-6565-5656-5-656565656-6-56565-6565656
-6-565-6565-56565-565-6565-5656-56-65656-5-656565656-565656
-6-6-56-6-5-6-65-5-656-565-5-656-65-6-656-6-6-5-5-6-5-6-6-5
-6-6-56-6-5-6-65-56-6-656-6-6-5-5-6-5-6-6-5656565-65656-5-5
-6-6-56-6-5-6-65-5656-5-656565656-6-5-5-6-6-656-656-5656565
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-6-6-56-65-6-5-565-6565-56-56-6-6565656-65-65-6-6-65656-5-5
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56-5-65-5-5-5-6-5-6-5-6-5-6-6-6-65-5-5656-65-5-56565-56-5-6
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56-5-65-5-6-56-6565-5-5656-5-5-6-5-5-5-6-5-6-6-56565-56-5-6
56-5-65-565-65-5-5-5-56-6-6565-56-56-6-5-6-5-65-5-5656-6565
56-5-65-565-65-5-5-5656-6-6565-56-56-6-5-6-5-65-5-5656-6565
56-56-5-6-65-5656-656565656-656565656-6-5-56565-6-6565-5656
56-56-5-6565-5656-656565656-656565656-6-5-56565-6-6565-5656
56-565-6565-5-65-5656565-6565656-6565-56-6-56-5-6-5-6-5-656
56-565-6565-5-65-5656565-6565656-6565-5656-56-5-6-5-6-5-656
56-565-6565-56565-565-6-65-5-656-565-5-656-65-656-5-6-5-5-6
56-565-6565-56565-565-6-65-56-656-5-6-5-5-6565656-56565-6-6
56-565-6565-56565-565-6-65-5656-5-656565656-6-56565-6565656
56-565-6565-56565-565-6-65-5656-56-65656-5-656565656-565656
56-565-6565-56565-565-6565-5-656-565-5-656-65-656-5-6-5-5-6
56-565-6565-56565-565-6565-56-656-5-6-5-5-6565656-56565-6-6
56-565-6565-56565-565-6565-5656-5-656565656-6-56565-6565656
56-565-6565-56565-565-6565-5656-56-65656-5-656565656-565656
56-6-56-6-5-6-65-5-656-565-5-656-65-6-656-6-6-5-5-6-5-6-6-5
56-6-56-6-5-6-65-56-6-656-6-6-5-5-6-5-6-6-5656565-65656-5-5
56-6-56-6-5-6-65-5656-5-656565656-6-5-5-6-6-656-656-5656565
56-6-56-6-5-6-65-5656-56-656-656-6-6-5-5-6-565656565-656565
56-6-56-6-5-6-65-5656-6565656-6-6-5-5-6-6-6-5656565-5-565-5
56-6-56-6-5-6565-5-656-565-5-656-65-6-656-6-6-5-5-6-5-6-6-5
56-6-56-6-5-6565-56-6-656-6-6-5-5-6-5-6-6-5656565-65656-5-5
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56-6-56-6-6-6-565-5-5-5-6-5-6-6-6565-5-656-565-5-656-65-5-5
56-6-56-6-6-6-565-5-5-5-6-5-6-6-6565-56-5-5656565-65656-5-5
56-6-56-6-6-6-565-5-5-565-56-656-5-5656-6-6-6-65-5-65656-65
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