positive definiteness of Hankel matrices

[deutsch]

A006762 is counting only polyominoes that are strictly 2-dimensional - 
it excludes those where all the squares are in a single line.  Thus, 
for n>1, A006762(n) = A001168(n) - 2.

Franklin T. Adams-Watters

-----Original Message-----
From: Tanya Khovanova <tanyakh at TanyaKhovanova.com>

A001168 Number of fixed polyominoes with n cells.
A006762 Number of fixed polyominoes with n cells.

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