#17594: iOA of type OA(k,n)-OA(k,u)-2.OA(k,1)
-------------------------------------+-------------------------------------
Reporter: ncohen | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.5
Component: combinatorial | Resolution:
designs | Merged in:
Keywords: | Reviewers:
Authors: Nathann Cohen | Work issues:
Report Upstream: N/A | Commit:
Branch: public/17594 | 311cd172c2cd1bdc90449f1f01931530b3f523b9
Dependencies: #17149 | Stopgaps:
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Comment (by ncohen):
Hello !
Sorry for this 'x': actually, I already fixed that in this ticket's
dependency #17149 (it is closed but not yet in a beta)
> It seems to work but we do have very few examples of `OA(k,n) -
OA(k,u)`, right?
> {{{
> sage: for n in range(2,1000):
> ....: if
designs.incomplete_orthogonal_array(4,n,[2],existence=True):
> ....: print n
> 9
> }}}
With this code you only test `OA(k,n)-OA(k,2)`. Try this:
{{{
sage: for i in range(2,1000):
....: for j in range(2,i):
....: if
designs.incomplete_orthogonal_array(4,i,[j],existence=True):
....: print "OA({},{})-OA({},{})".format(4,i,4,j)
....:
OA(4,9)-OA(4,2)
OA(4,16)-OA(4,3)
OA(4,17)-OA(4,4)
OA(4,25)-OA(4,6)
OA(4,26)-OA(4,5)
OA(4,30)-OA(4,5)
OA(4,36)-OA(4,5)
OA(4,36)-OA(4,7)
OA(4,37)-OA(4,6)
OA(4,41)-OA(4,10)
OA(4,42)-OA(4,7)
...
}}}
If you have a hole of size 3 in an OA, you do not necessarily have a hole
of size 2. It's not a `-2.OA(k,1)`, it's a `-OA(k,2)`!
Nathann
--
Ticket URL: <http://trac.sagemath.org/ticket/17594#comment:9>
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