Some counting problems
In his invited lecture "Chemical Isomerism, a Challenge for
Algebraic Combinatorics and for Computer Science" at the AAECC-11
A. Kerber  said:
[...] The existence of chemical isomerism
was stated by the end of the eighteenth century,
it was verified a quarter of a century later and
explained another half of a century afterwards.
It stimulated the development of graph theory and gave
birth to algebraic combinatorics. [...]
The most famous starting point for enumeration under group action
is  in which Pólya not only describes
cycle index techniques for determining the numbers of orbits under
finite group actions, but he demonstrates how to apply these methods
for the chemical problem of isomer enumeration as well.
last changed: January 23, 2001