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URL: https://oeis.org/A006680

⇱ A006680 - OEIS

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A006680
Number of binary phylogenetic trees with n labels.
1
1, 1, 7, 45, 465, 5775, 88515, 1588545, 32852925, 768242475, 20053670175, 577971719325, 18230691904425, 624676513836375, 23106221910646875, 917643290676737625, 38944796393877499125, 1759004961887566267875
OFFSET
2,3
REFERENCES
Foulds, L. R.; Robinson, R. W. Enumeration of binary phylogenetic trees. Combinatorial mathematics, VIII (Geelong, 1980), pp. 187-202, Lecture Notes in Math., 884, Springer, Berlin-New York, 1981. Math. Rev. 83a:05071.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
L. R. Foulds and R. W. Robinson, Enumeration of binary phylogenetic trees, pp. 187-202, Lecture Notes in Math., 884, Springer, Berlin-New York, 1981. (Annotated scanned copy)
FORMULA
a(2) = 1, a(n) = A006678(n-1) + 2*(n-1)*A006678(n-2) - (n+1)*a(n-1) for n >= 3. - Sean A. Irvine, Jun 16 2017
CROSSREFS
Sequence in context: A071971 A370253 A337553 * A197796 A197856 A205080
KEYWORD
nonn
EXTENSIONS
More terms and offset corrected by Sean A. Irvine, Jun 16 2017
STATUS
approved