%I #13 Apr 06 2020 12:33:07
%S 1,2,10,40,185,828,3805,17411,80177,369675,1710173,7931011,36884730,
%T 171987194,804027444,3767994408,17699839325,83328339997,393123808821,
%U 1858351499207,8801160980038,41756069328689,198437460900302,944521149228740,4502419787519360
%N Number of polyhexes of class PF2.
%C See reference for precise definition.
%C Cyvin has incorrect a(13)=369639 and a(14)=1710137 in Table III due to using incorrect values for A026298(13) and A026298(14) in Table II. - _Sean A. Irvine_, Apr 02 2020
%H S. J. Cyvin, Zhang Fuji, B. N. Cyvin, Guo Xiaofeng, and J. Brunvoll, <a href="https://doi.org/10.1021/ci00009a021">Enumeration and classification of benzenoid systems. 32. Normal perifusenes with two internal vertices</a>, J. Chem. Inform. Comput. Sci., 32 (1992), 532-540.
%F a(4)=1, a(n) = A026106(n) + A026118(n) + A026298(n) + A030519(n) for n > 4. - _Sean A. Irvine_, Apr 02 2020
%Y Cf. A026106, A026118, A026298, A030519, A030520, A030525, A030529, A030532, A030534.
%K nonn
%O 4,2
%A _N. J. A. Sloane_
%E a(13) and a(14) corrected and more terms from _Sean A. Irvine_, Apr 02 2020