id:A144757 - OEIS Search Results

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Number of factor trees for n.

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1, 1, 1, 1, 2, 1, 2, 1, 2, 1, 6, 1, 2, 2, 5, 1, 6, 1, 6, 2, 2, 1, 20, 1, 2, 2, 6, 1, 12, 1, 14, 2, 2, 2, 30, 1, 2, 2, 20, 1, 12, 1, 6, 6, 2, 1, 70, 1, 6, 2, 6, 1, 20, 2, 20, 2, 2, 1, 60, 1, 2, 6, 42, 2, 12, 1, 6, 2, 12, 1, 140, 1, 2, 6, 6, 2, 12, 1, 70, 5, 2, 1, 60, 2, 2, 2, 20, 1, 60, 2, 6, 2, 2, 2, 252 (list; graph; listen)

	OFFSET	`2,5`
	COMMENT	`A factor tree for n is a binary tree, with the root labeled with n and the terminal nodes labeled with primes, such that each non-terminal node is the product of its two child nodes. This is the number of prime factorizations of n, ignoring the commutativity and associativity of multiplication.`
	EXAMPLE	`a(12)=6 because 12 can be factored as (22)3, (23)2, (32)2, 2(23), 2(32) and 3(22).`
	CROSSREFS	`a(n) = A000108(A001222(n)-1) * A008480(n)` `Sequence in context: A020738 A063279 A124333 this_sequence A002107 A133099 A006571` `Adjacent sequences: A144754 A144755 A144756 this_sequence A144758 A144759 A144760`
	KEYWORD	`easy,nonn`
	AUTHOR	`David Radcliffe (radcl008(AT)umn.edu), Sep 20 2008`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

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