Table 1. Number of Gaseous and Protonated Structural Alkene Isomers for a Given Total Carbon Length.

alkene carbon length	number of gaseous structural isomers	number of protonated structural isomers (no primary)
3	1	1
6	13	9
9	153	122
12	2281	1819
13	5690	4852
14	14 397	11 602
15	36 562	29 623
16	93 646	76 037