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Search: id:A008479
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| A008479 |
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Number of numbers <= n with same prime factors as n. |
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+0
7
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| 1, 1, 1, 2, 1, 1, 1, 3, 2, 1, 1, 2, 1, 1, 1, 4, 1, 3, 1, 2, 1, 1, 1, 4, 2, 1, 3, 2, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 1, 3, 1, 1, 1, 2, 2, 1, 1, 6, 2, 4, 1, 2, 1, 7, 1, 3, 1, 1, 1, 2, 1, 1, 2, 6, 1, 1, 1, 2, 1, 1, 1, 8, 1, 1, 3, 2, 1, 1, 1, 5, 4, 1, 1, 2, 1, 1, 1, 3, 1, 3, 1, 2, 1, 1, 1, 9
(list; graph; listen)
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OFFSET
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1,4
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REFERENCES
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Problem 5735, Amer. Math. Monthly, 78 (1971), 680-681. (Incorrect!)
Problem 5735, Amer. Math. Monthly, 97 (1990), 937.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..10000
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MATHEMATICA
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PkTbl=Prepend[ Array[ Times @@ First[ Transpose[ FactorInteger[ # ] ] ]&, 100, 2 ], 1 ]; 1+Array[ Count[ Take[ PkTbl, #-1 ], PkTbl[ [ # ] ] ]&, Length[ PkTbl ] ]
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CROSSREFS
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Cf. A005361, A007947.
Sequence in context: A072411 A091050 A005361 this_sequence A107345 A000688 A038538
Adjacent sequences: A008476 A008477 A008478 this_sequence A008480 A008481 A008482
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KEYWORD
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nonn,easy
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AUTHOR
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Jeffrey Shallit, Olivier Gerard (olivier.gerard(AT)gmail.com)
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