id:A162306 - OEIS Search Results

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Irregular triangle in which row n contains the numbers whose prime factors are a subset of prime factors of n.

+0
2

1, 1, 2, 1, 3, 1, 2, 4, 1, 5, 1, 2, 3, 4, 6, 1, 7, 1, 2, 4, 8, 1, 3, 9, 1, 2, 4, 5, 8, 10, 1, 11, 1, 2, 3, 4, 6, 8, 9, 12, 1, 13, 1, 2, 4, 7, 8, 14, 1, 3, 5, 9, 15, 1, 2, 4, 8, 16, 1, 17, 1, 2, 3, 4, 6, 8, 9, 12, 16, 18, 1, 19, 1, 2, 4, 5, 8, 10, 16, 20, 1, 3, 7, 9, 21, 1, 2, 4, 8, 11, 16, 22, 1, 23 (list; graph; listen)

	OFFSET	`1,3`
	COMMENT	`Row n begins with 1, ends with n, and has A010846(n) terms.`
	LINKS	`T. D. Noe, Rows n=1..200 of triangle, flattened`
	MATHEMATICA	`pf[n_] := If[n==1, {}, Transpose[FactorInteger[n]][[1]]]; SubsetQ[lst1_, lst2_] := Intersection[lst1, lst2]==lst1; Flatten[Table[pfn=pf[n]; Select[Range[n], SubsetQ[pf[ # ], pfn] &], {n, 27}]]`
	CROSSREFS	`Sequence in context: A144113 A165416 A057059 this_sequence A027750 A087295 A130517` `Adjacent sequences: A162303 A162304 A162305 this_sequence A162307 A162308 A162309`
	KEYWORD	`nonn`
	AUTHOR	`T. D. Noe (noe(AT)sspectra.com), Jun 30 2009`

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

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