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A162306
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Irregular triangle in which row n contains the numbers whose prime factors are a subset of prime factors of n.
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2
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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; refs; listen; history; internal format)
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OFFSET
| 1,3
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COMMENTS
| Row n begins with 1, ends with n, and has A010846(n) terms.
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LINKS
| T. D. Noe, Rows n=1..200 of triangle, flattened
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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}]]
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CROSSREFS
| Sequence in context: A165416 A057059 A169896 * A027750 A087295 A175344
Adjacent sequences: A162303 A162304 A162305 * A162307 A162308 A162309
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KEYWORD
| nonn,tabf
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AUTHOR
| T. D. Noe (noe(AT)sspectra.com), Jun 30 2009
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