[r-t] Bobs only Erin Triples (was: Composition search)

[Matthew Frye]

> On 4 Dec 2015, at 19:07, Ian Broster <ian at broster.co.uk> wrote:
> 
> > There are 26, excluding rotations.
> 
> I think that there are 140. I made a list once, but lost it long ago. Luckily the internet archive to the rescue!
> 
> https://web.archive.org/web/20050426201814/http://www-users.cs.york.ac.uk/~ianb/solid/plainbobminorbobs.text <https://web.archive.org/web/20050426201814/http://www-users.cs.york.ac.uk/~ianb/solid/plainbobminorbobs.text> 

OK, taking that list as definitive, a little dab of python finds three unique 360’s:
Final list:  ['bbpbbpbpbppbbpbppbbppbbpbbpppp', 'bbpbppbbppbpbppppbbpppbpbbpppp', 'bbpppbppppbbpppbppppbbpppbpppp’]

The one I didn’t give previously can be thought of as WHW with an extra Q-set, giving, eg. WFWHWWOHWIHW, where 7 leads (and HW) have been removed from the first part and inserted in the third part by the F/O/I Q-set. I *think* I knew about this, but forgot it because it’s not a very nice compared to the other two, imho.

Point is, I have no idea how extensive a tree-search is needed for this problem, but such a strategy is probably beyond pencil and paper in reasonable time? Whereas I was able to do it as a teenager in a couple of hours with some basic Q-set considerations.

MF
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://bellringers.net/pipermail/ringing-theory/attachments/20151204/ead582d0/attachment-0003.html>