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A034941 Number of labeled triangular cacti with 2n+1 nodes (n triangles). 5
1, 1, 15, 735, 76545, 13835745, 3859590735, 1539272109375, 831766748637825, 585243816844111425, 5200382401889350425750, 569585968715180280038175 (list; graph; refs; listen; history; internal format)
OFFSET

0,3

LINKS

Index entries for sequences related to cacti

FORMULA

A034940/(2n+1).

The closed form a(n) = (2n-1)!! (2n+1)^(n-1) can be obtained from the generating function in A034940. - Noam D. Elkies (elkies(AT)math.harvard.edu), Dec 16 2002

EXAMPLE

E.g. a(3) = 5!! 7^2 = (1*3*5) * 49 = 735.

CROSSREFS

Cf. A003081.

Sequence in context: A062032 A204251 A117812 * A199227 A055683 A196465

Adjacent sequences:  A034938 A034939 A034940 * A034942 A034943 A034944

KEYWORD

nonn

AUTHOR

Christian G. Bower (bowerc(AT)usa.net), Oct 15 1998.

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Last modified February 15 21:56 EST 2012. Contains 205860 sequences.