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A036758
Number of edge-rooted tree-like octagonal systems.
12
1, 5, 31, 216, 1617, 12705, 103358, 863161, 7357277, 63747221, 559809997, 4971528380, 44572279612, 402883616972, 3667455453895, 33592221383213, 309375866119789, 2863158467711801, 26613026976466819, 248338952866938164, 2325603300814424911, 21848776123428594487
OFFSET
1,2
REFERENCES
S. J. Cyvin, B. N. Cyvin, and J. Brunvoll, Enumeration of tree-like octagonal systems: catapolyoctagons, ACH Models in Chem. 134(1) (1997), 55-70.
LINKS
J. Brunvoll, S. J. Cyvin, and B. N. Cyvin, Enumeration of tree-like octagonal systems, J. Math. Chem. 21 (1997), 193-196; see Section 3 (p. 194).
FORMULA
G.f. G(x) = G satisfies G = x * (1 + 5*G + 6*G^2 + G^3).
a(r) = A121112(r) + A121113(r) + A121114(r) for r >= 2. - Petros Hadjicostas, Jul 30 2019
MAPLE
Order := 30: S := solve(series(G/(1+5*G+6*G^2+G^3), G)=x, G);
CROSSREFS
KEYWORD
nonn,easy
EXTENSIONS
More terms from Emeric Deutsch, Feb 28 2004
STATUS
approved