A007098 Number of unlabeled bisectable trees with 2n+1 nodes.
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
Offset: 0
Keywords
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
Crossrefs
Cf. A228601.
Formula
a(n) = Sum_{k=1..n} binomial(k + 1, 2) * A228601(n, k). - Sean A. Irvine, Oct 10 2017
Extensions
a(23) onwards added by N. J. A. Sloane, Oct 19 2006 from the Robinson reference