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A039658 Related to enumeration of edge-rooted catafusenes. 7
0, 1, 2, 5, 8, 18, 28, 64, 100, 237, 374, 917, 1460, 3679, 5898, 15183, 24468, 64055, 103642, 275011, 446380, 1197616, 1948852, 5277070, 8605288, 23483743, 38362198, 105392983, 172423768, 476459938, 780496108, 2167743688, 3554991268 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
From Petros Hadjicostas, Jan 13 2019: (Start)
This sequence appears in Table I, p. 533, in Cyvin et al. (1992) and Table I, p. 1174, in Cyvin et al. (1994).
In Cyvin et al. (1992), it is defined through eq. (22), p. 535. We have a(n) = Sum_{i=1..n-1} M(i)*M(n-i), where M(2*n) = M(2*n-1) = A007317(n) for n >= 1.
In Cyvin et al. (1992), it is used in the calculation of sequence A026118. See eq. (34), p. 536, in Cyvin et al. (1992).
(The word "annelated" in the title of Cyvin et al. (1994) is spelled "annealated" in the text of Cyvin et al. (1992).)
(End)
LINKS
S. J. Cyvin, Zhang Fuji, B. N. Cyvin, Guo Xiaofeng, and J. Brunvoll, Enumeration and classification of benzenoid systems. 32. Normal perifusenes with two internal vertices, J. Chem. Inform. Comput. Sci., 32 (1992), 532-540.
S. J. Cyvin, B. N. Cyvin, J. Brunvoll, and E. Brendsdal, Enumeration and classification of certain polygonal systems representing polycyclic conjugated hydrocarbons: annelated catafusenes, J. Chem. Inform. Comput. Sci., 34 (1994), 1174-1180.
Eric Weisstein's World of Mathematics, Fusenes.
Eric Weisstein's World of Mathematics, Polyhex.
FORMULA
G.f.: (1+x)*(1 - 3*x^2 - sqrt(1 - 6*x^2 + 5*x^4))/(2*x^2*(1-x)) (eq. (9), p. 1175, in Cyvin et al. (1994)).
For n >= 1, a(n) = Sum_{i=1..n-1} A007317(floor((i+1)/2)) * A007317(floor((n-i+1)/2)). - Petros Hadjicostas, Jan 13 2019
MATHEMATICA
Rest[CoefficientList[Series[(1+x) (1-3x^2-Sqrt[1-6x^2+5x^4])/(2x^2 (1-x)), {x, 0, 40}], x]] (* Harvey P. Dale, Oct 30 2016 *)
CROSSREFS
Sequence in context: A293830 A073708 A024460 * A063675 A000943 A304966
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Emeric Deutsch, Mar 14 2004
STATUS
approved

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Last modified March 18 22:56 EDT 2024. Contains 370952 sequences. (Running on oeis4.)