id:A034941 - OEIS Search Results

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Number of labeled triangular cacti with 2n+1 nodes (n triangles).

+0
3

1, 1, 15, 735, 76545, 13835745, 3859590735, 1539272109375, 831766748637825, 585243816844111425, 5200382401889350425750, 569585968715180280038175 (list; graph; listen)

	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 = (135) * 49 = 735.`
	CROSSREFS	`Cf. A003081.` `Sequence in context: A062079 A062032 A117812 this_sequence A055683 A116094 A020240` `Adjacent sequences: A034938 A034939 A034940 this_sequence A034942 A034943 A034944`
	KEYWORD	`nonn`
	AUTHOR	`Christian G. Bower (bowerc(AT)usa.net), Oct 15 1998.`

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Last modified December 6 22:55 EST 2009. Contains 170429 sequences.

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