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 A007098 Number of unlabeled bisectable trees with 2n+1 nodes. (Formerly M2596) 2
 1, 1, 3, 6, 19, 47, 140, 374, 1082, 2998, 8574, 24130, 68876, 195587, 559076, 1596651, 4575978, 13122219, 37711998, 108488765, 312577827, 901531937, 2603264050, 7524331268, 21768850808, 63032844756, 182662328945, 529722408615, 1537261773438 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 REFERENCES R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1980. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS R. W. Robinson, Table of n, a(n) for n = 0..99 F. Harary, R. W. Robinson, Isomorphic factorizations VIII: bisectable trees, Combinatorica 4 (2) (1984) 169-179. Index entries for sequences related to trees FORMULA a(n) = Sum_{k=1..n} binomial(k + 1, 2) * A228601(n, k). - Sean A. Irvine, Oct 10 2017 CROSSREFS Cf. A228601. Sequence in context: A347685 A219286 A104264 * A226322 A148566 A148567 Adjacent sequences: A007095 A007096 A007097 * A007099 A007100 A007101 KEYWORD nonn AUTHOR N. J. A. Sloane, Mira Bernstein EXTENSIONS a(23) onwards added by N. J. A. Sloane, Oct 19 2006 from the Robinson reference STATUS approved

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Last modified October 4 15:30 EDT 2023. Contains 365885 sequences. (Running on oeis4.)