id:A131893 - OEIS Search Results

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a(n) is the number of shapes of balanced trees with constant branching factor 7 and n nodes. The node is balanced if the size, measured in nodes, of each pair of its children differ by at most one node.

+0
5

1, 7, 21, 35, 35, 21, 7, 1, 49, 1029, 12005, 84035, 352947, 823543, 823543, 17294403, 155649627, 778248135, 2334744405, 4202539929, 4202539929, 1801088541, 21012699645, 105063498225, 291843050625, 486405084375, 486405084375 (list; graph; listen)

	OFFSET	`1,2`
	LINKS	`Jeffrey A. Barnett Counting Balanced Tree Shapes.`
	FORMULA	`a(0) = a(1) = 1; a(7n+1+m) = (7 choose m) * a(n+1)^m * a(n)^(7-m), where n >= 0 and 0 <= m <= 7.`
	CROSSREFS	`Cf. A110316, A131889, A131890, A131891, A131892.` `Sequence in context: A015729 A001485 A087111 this_sequence A045849 A031008 A147587` `Adjacent sequences: A131890 A131891 A131892 this_sequence A131894 A131895 A131896`
	KEYWORD	`easy,nonn`
	AUTHOR	`Jeffrey A. Barnett (jbb(AT)notatt.com), Jul 24 2007`

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Last modified December 15 00:47 EST 2009. Contains 170825 sequences.

AT&T Labs Research