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%I #5 Feb 27 2015 21:21:36
%S 2,6,20,70,252,894,3432,12870,48620,149226
%N The number of Kekulé structures of the rhombus-shaped benzenoid hydrocarbons.
%C Here n is the number of aromatic sextets.
%D I. Gutman, N. Turkovic and B. Furtula, "On distribution of pi electrons in rhombus-shaped benzenoid hydrocarbons", Indian Journal of Chemistry, Vol. 45A (2006), pp. 1601-1604. See Table 1 on page 1602.
%e If n=1 then the number of Kekulé structures of the rhombus-shaped benzenoid hydrocarbons is 2.
%e If n=2 then the number of Kekulé structures of the rhombus-shaped benzenoid hydrocarbons is 6.
%e If n=3 then the number of Kekulé structures of the rhombus-shaped benzenoid hydrocarbons is 20.
%K nonn
%O 1,1
%A _Parthasarathy Nambi_, Aug 23 2007