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%I M2596 #17 Oct 11 2017 05:23:12
%S 1,1,3,6,19,47,140,374,1082,2998,8574,24130,68876,195587,559076,
%T 1596651,4575978,13122219,37711998,108488765,312577827,901531937,
%U 2603264050,7524331268,21768850808,63032844756,182662328945,529722408615,1537261773438
%N Number of unlabeled bisectable trees with 2n+1 nodes.
%D R. W. Robinson, Numerical implementation of graph counting algorithms, AGRC Grant, Math. Dept., Univ. Newcastle, Australia, 1980.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H R. W. Robinson, <a href="/A007098/b007098.txt">Table of n, a(n) for n = 0..99</a>
%H F. Harary, R. W. Robinson, <a href="http://dx.doi.org/10.1007/BF02579217">Isomorphic factorizations VIII: bisectable trees</a>, Combinatorica 4 (2) (1984) 169-179.
%H <a href="/index/Tra#trees">Index entries for sequences related to trees</a>
%F a(n) = Sum_{k=1..n} binomial(k + 1, 2) * A228601(n, k). - _Sean A. Irvine_, Oct 10 2017
%Y Cf. A228601.
%K nonn
%O 0,3
%A _N. J. A. Sloane_, _Mira Bernstein_
%E a(23) onwards added by _N. J. A. Sloane_, Oct 19 2006 from the Robinson reference
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