Enumeration under Group Equivalences

Then Polya s renowned Haupt Satz gives the various ( ) as the coefficients of YiaeLt a in Z[G z]. For example, for the ethylene skeleton (with the 4 H-atoms marking the substitution positions), as 

The isomer counts are in this case readily obtainable even without knowledge of Polya theory, but the method extends to rather much more comphcated skeletons. If one were to wish not to distinguish cis and trans structures, then the group would be extended to A U (12)A- 

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