[seqfan] Generalization of A005646

Robert Munafo mrob27 at gmail.com
Sat Jan 2 00:24:22 CET 2010

You say "more than 2-way partitions are allowed".

Is it also required that each partition is 3-way, or can it be a mix of
partitions of 2-way and/or 3-way?

(If the former, I suppose the value would be 0 for N=1, *undefined* for N=2,
and 1 for N-3)

Franklin T. Adams-Watters wrote:

> I'm interested in generalizing A005646, and the associated triangle, to the
> case where more than 2-way partitions are allowed in making the
> classification.  We would want to require that each partition be completely
> essential; that is, combining any two parts in any partition would result in
> at least one pair of points being indistinguishable.
> I don't have enough terms to even try looking this up to see if it is in
> the OEIS; I believe that it starts (from n = 1):
> 1,1,2,5
> If it is present, it has neither a link to nor from A005646.
> More terms, anyone?  Is there any literature on this question?

Robert Munafo  --  mrob.com

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