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 A221043 The hyper-Wiener index of the Bethe cactus lattice graph D_n defined pictorially in the Hosoya - Balasubramanian reference. 1
 10, 457, 11788, 223306, 3527782, 49658659, 646456696, 7958918644, 94000489378, 1075247030365, 11991524116804, 131012134626814, 1407240945512638, 14901372361780855, 155885329216404592, 1613748977026119016, 16554187553043529402, 168462466522953130609 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..18. K. Balasubramanian, Recent developments in tree-pruning methods and polynomials for cactus graphs and trees, J. Math. Chemistry, 4 (1990) 89-102. H. Hosoya and K. Balasubramanian, Exact dimer statistics and characteristic polynomials of cacti lattices, Theor. Chim. Acta 76 (1989) 315-329. Also on ResearchGate. Index entries for linear recurrences with constant coefficients, signature (37,-549,4185,-17523,40095,-45927,19683). FORMULA a(n) = -(7/8)+3^n*(2*n^2-(9/4)*n-10)+3^(2*n)*(4*n^2-(41/4)*n+(87/8)). G.f.: x*(243*x^4+3807*x^3-369*x^2-87*x-10) / ((x-1)*(3*x-1)^3*(9*x-1)^3). [Colin Barker, Jan 01 2013] MAPLE a := proc (n) options operator, arrow: -7/8+3^n*(2*n^2-(9/4)*n-10)+3^(2*n)*(4*n^2-(41/4)*n+87/8) end proc: seq(a(n), n = 1 .. 18); CROSSREFS Cf. A221042. Sequence in context: A304289 A217523 A232773 * A337757 A288548 A289030 Adjacent sequences: A221040 A221041 A221042 * A221044 A221045 A221046 KEYWORD nonn,easy AUTHOR Emeric Deutsch, Dec 30 2012 EXTENSIONS Offset changed from 0 to 1 by Bruno Berselli, Dec 30 2012 STATUS approved

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Last modified May 21 01:24 EDT 2024. Contains 372720 sequences. (Running on oeis4.)