[r-t] Minor principles (MUG)

Philip Saddleton pabs at cantab.net
Sun Sep 5 10:33:27 UTC 2004

Alexander Holroyd <holroyd at math.ubc.ca> wrote at 13:42:34 on Sat, 4 Sep 
>One mystery (to me) is how you managed to get those 1/2 characters in an

I typed them into word then pasted them into Turnpike.

>One idea might be to start with an extent of Brussels Sprout
>(&- 2, bob=34), split it into whole leads at the p.n. 1, and
>reverse half of the leads so that fours come adjacent to each other to
>make eights....

The extent of Brussels Sprout uses the Hudson Group. There are four 
isomorphisms that give a set of 60 true leads, but in each case the 
group contains only one possible change to link leads - 14 (twice), 36 
or 16. The last of these gives 10 true courses that cannot be joined at 
the lead end:

123456 124563
136524 135246
164235 162354
145362 143625
152643 156432

The others give B-blocks containing between them four of the six leads 
with a particular pair in 56 (or 12) - again these cannot be joined with 
calls at the lead end.


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