id:A016021 - OEIS Search Results

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Number of permutations of {1,2,...,n} in which each element follows its proper divisors.

+0
1

1, 1, 1, 2, 3, 12, 25, 150, 378, 1960, 8154, 81540, 261250, 3135000, 19358040, 160331626, 719579700, 11513275200, 62702704800, 1128648686400, 7122671957664, 88475482100520, 905279068633800, 19916139509943600 (list; graph; listen)

	OFFSET	`0,4`
	EXAMPLE	`12 valid permutations for a(5): 12345 12354 12435 12453 12534 12543 13245 13254 13524 15234 15243 15324`
	CROSSREFS	`Sequence in context: A084728 A099429 A049601 this_sequence A136703 A075269 A089414` `Adjacent sequences: A016018 A016019 A016020 this_sequence A016022 A016023 A016024`
	KEYWORD	`nonn`
	AUTHOR	`David W. Wilson (davidwwilson(AT)comcast.net), Jun 07 2000`

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Last modified August 19 23:53 EDT 2008. Contains 142930 sequences.

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