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

[hv at crypt.org]

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) = ...

Hugo