[seqfan] Correcting A002932 (n-step walks on square lattice)
Joseph S. Myers
jsm at polyomino.org.uk
Mon Nov 22 14:24:38 CET 2010
A002932 is "Number of n-step walks on square lattice." - where there is a
restriction (see the Fisher and Hiley reference) that no lattice point
appears more than once in the path, and no two points in the path that are
not consecutive in the path may be adjacent in the lattice.
There are two entries in the "formula" section both of which are wrong -
one reporting an observed link to A001333 and the other giving an explicit
formula; they go wrong from the term with value 940 onwards, where both
give the value 956 instead. (They would probably be correct if the
adjacency restriction was local, only relating to points 3 apart in the
path, though I haven't checked this.)
The last term given of the sequence, 396204, disagrees with my
calculations; I get 396172 although my program agrees with the earlier
terms. Before I make corrections (and extensions - I have eight more
terms) to this sequence, could someone confirm whether they get the figure
I do or the figure in the sequence (which is accurately transcribed from
the Fisher and Hiley reference)?
--
Joseph S. Myers
jsm at polyomino.org.uk
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