Stacking sequences, anybody?

[Antti Karttunen]

"Stacking sequences" just popped up, when I was googling for something
else. They seem to occur in metallurgy and related fields:
http://www.google.com/search?hl=en&lr=&q=%22stacking+sequences%22&btnG=Search

see e.g. http://metalrg.iisc.ernet.in/~lord/vop.pdf
("Stacking sequences and symmetry properties of trigonal vacancy-ordered 
phases (tau phases)")

Are these related to coordination sequences for zeolites? In any case, 
related to crystal-structures
of certain minerals, unless I got it all wrong. I'm not a chemist...

Just a hint for somebody with extra time. The mathematics don't seem too 
complex.


Terveisin,

Antti