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 A216108 The Wiener index of the ortho-polyphenyl chain with n hexagons (see the Dou et al. and the Deng references). 5
 27, 198, 585, 1260, 2295, 3762, 5733, 8280, 11475, 15390, 20097, 25668, 32175, 39690, 48285, 58032, 69003, 81270, 94905, 109980, 126567, 144738, 164565, 186120, 209475, 234702, 261873, 291060, 322335, 355770 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The Hosoya-Wiener polynomial of the graph is n(6+6t+6t^2+3t^3)+(1+2t+2t^2+t^3)^2*(t^{2n+1}-nt^3+nt-t)/(t^2-1)^2. REFERENCES Y. Dou, H. Bian, H. Gao, and H. Yu, The polyphenyl chains with extremal edge-Wiener indices, MATCH Commun. Math. Comput. Chem., 64, 2010, 757-766. LINKS H. Deng,  Wiener indices of spiro and polyphenyl hexagonal chains, arXiv:1006.5488 Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1). FORMULA a(n) = 12n^3+36n^2-21n. G.f.: -9*x*(5*x^2-10*x-3)/(x-1)^4. [Colin Barker, Oct 30 2012] EXAMPLE a(1)=27 because we have only 1 hexagon with Wiener index 6*1 + 6*2 + 3*3 = 27. MAPLE seq(12*n^3+36*n^2-21*n, n=1..30); MATHEMATICA LinearRecurrence[{4, -6, 4, -1}, {27, 198, 585, 1260}, 30] (* Jean-François Alcover, Sep 23 2017 *) CROSSREFS Cf. A216109, A216110, A216111, A216112, A216113. Sequence in context: A228463 A000499 A042416 * A216110 A216112 A183596 Adjacent sequences:  A216105 A216106 A216107 * A216109 A216110 A216111 KEYWORD nonn,easy AUTHOR Emeric Deutsch, Oct 26 2012 STATUS approved

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Last modified December 15 09:05 EST 2019. Contains 329995 sequences. (Running on oeis4.)