[seqfan] Re: 2-d partitions, rotationally symmetric pieces

hv at crypt.org hv at crypt.org
Tue Mar 24 00:39:43 CET 2009

hv at crypt.org wrote:
:All the points below involve connected pieces consisting of unit squares
:cut along lattice lines, as 2-d analogues of the integers used for partitions.
:1. A078469 "Number of different compositions of the ladder graph L_n."
:This is identically the number of partitions of the 2 x n rectangle.
:I feel the entry for a(0) = 0 should be 1 instead, though it does throw
:out the start of the recurrence.

There is also a typo in the formula line:
   a(n+2) = 6*a(n-1)+a(n-2). G.f.: 2*x/(1-6*x-x^2).
which should read:
   a(n) = ...


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