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%I #9 Sep 06 2017 21:18:00
%S 9,104,3724,152978,6772428,318919354,15762420826,808272767014,
%T 42631956711628,2298618088718378,126131492134695474,
%U 7020934326396461014,395480502329858803674,22501172037539767125398
%N Kekulé numbers for certain benzenoids of trigonal symmetry.
%D S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (see p. 313).
%H G. C. Greubel, <a href="/A110698/b110698.txt">Table of n, a(n) for n = 0..550</a>
%F a(n) = 20*binomial(2n, n)^3 - 18*binomial(2n, n)^2 + 9*binomial(2n, n) - 2.
%p a:=n->20*binomial(2*n,n)^3-18*binomial(2*n,n)^2+9*binomial(2*n,n)-2; seq(a(n),n=0..16);
%t Table[20*Binomial[2*n, n]^3 - 18*Binomial[2*n, n]^2 + 9*Binomial[2*n, n] - 2, {n,0,50}] (* _G. C. Greubel_, Sep 06 2017 *)
%o (PARI) for(n=0,25, print1(20*binomial(2n, n)^3 - 18*binomial(2n, n)^2 + 9*binomial(2n, n) - 2, ", ")) \\ _G. C. Greubel_, Sep 06 2017
%K nonn
%O 0,1
%A _Emeric Deutsch_, Aug 03 2005
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