Table 3. Degeneracies of the top three most important structures of n-acene as a function of the acene length n.

n	Most important	Second most important	Third most important
3	3	1	0
4	4	6	0
5	5	20	1
6	6	50	10
7	7	105	53
8	8	196	200
9	9	336	606
10	10	540	1572
11	11	825	3630
12	12	1210	7656
13	13	1716	15015
14	14	2366	27742
15	15	3185	48763
16	16	4200	82160
17	17	5440	133484
18	18	6936	209924
19	19	8721	321091
20	20	10830	479586

Here the most important structure is the Kekulé structure with one aromatic sextet, the second most important structure is the non-Kekulé structure with two aromatic sextets and two unpaired π-electrons, and the third most important structure is the non-Kekulé structure with four aromatic sextets and four unpaired π-electrons.