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 A058866 Number of 2-trees rooted at a edge. 8
 1, 2, 6, 21, 83, 356, 1599, 7434, 35381, 171508, 843419, 4197179, 21094355, 106915928, 545859112, 2804656069, 14491370996, 75248398034, 392476363133, 2055245992376, 10801442696736, 56953957110855, 301207378815752 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 75, Eq. (3.5.11). LINKS FORMULA H. and P. give g.f. CROSSREFS Let A063687(n) be the number of 2-trees rooted at a symmetric edge (see H. and P. Eq. (3.5.9)). Then A058866(n) = A058870(n) + A063687(n). Cf. A058870, A058870, A054581. Sequence in context: A148495 A150221 A063689 * A178325 A087649 A328435 Adjacent sequences:  A058863 A058864 A058865 * A058867 A058868 A058869 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Jan 06 2001 EXTENSIONS More terms from Vladeta Jovovic, Aug 22 2001 STATUS approved

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Last modified November 29 07:44 EST 2020. Contains 338756 sequences. (Running on oeis4.)