[seqfan] Problem with consistency of A086581

David Scambler dscambler at bmm.com
Fri Mar 25 03:22:17 CET 2011


Sequence A086581<https://oeis.org/A086581> has inconsistent name/offset/data/formula/example.

The name is "Number of Dyck paths of semilength n with no UUDD" with offset 0,
commencing 1, 1, 2, 5, 13,...

This would be correct if any of the following changes were made:


1)      Name change to "Number of Dyck paths of semilength n with no DDUU"

2)      Offset change to 1, or

3)      Data change to 1, 1, 1, 2, 5, 13,...

However the formulas from Paul Barry matche the data and offset,
whereas the example from  Emeric Deutsch matches what the sequence claims to be.

The easiest fix-all would be to change the name to
"Number of Dyck paths of semilength n+1 with no UUDD" but that is not as
elegant as the existing name.

Several changes need to be made. Any suggestions?

dave



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