Traditional methods for counting position isomers, meso and enantiomeric structures of organic compounds are costumarily based on the classical method of group action leading to the determination of a cycle index convertible into a counting polynomial. The innovative approach presented in this book considers a homopolysubstitution as a Young’s Partition including combinations of mono-, gem di- and gem tri-substitutions which are distributed in distinct ways among numerous carbon atoms. The resulting arrangements obtained are used to build up algorithms for enumerating permutomers, meso isomers and enantiomers of series of homopolysubstituted n-alkanes (HPSNAs) with any size. This vision shows the close link existing between stereochemistry and combinatorics and provides new mathematical solutions that should be useful to students, teachers, researchers and professionals in chemistry and biochemistry or to anyone else who may utilize such pattern inventories for isomer enumeration, structural analyses, molecular design or other chemical investigations.