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Search: id:A071834
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| A071834 |
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Numbers n such that n and sigma(n) have the same largest prime factor. |
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+0
1
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| 6, 28, 40, 84, 117, 120, 135, 140, 224, 234, 270, 420, 468, 496, 585, 672, 756, 775, 819, 891, 931, 936, 1080, 1120, 1170, 1287, 1372, 1488, 1550, 1625, 1638, 1782, 1862, 2176, 2299, 2325, 2340, 2480, 2574, 2793, 3100, 3159, 3250, 3276, 3360, 3472
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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n such that A006530(n)=A006530(sigma(n))
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EXAMPLE
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1550 = 2.5^2.31 and sigma(1550) = 2976 = 2^5.3.31 hence 1550 is in the sequence
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MAPLE
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for(n=2, 1000, if(component(component(factor(n), 1), omega(n))==component(component(factor(sigma(n)), 1), omega(sigma(n))), print1(n, ", ")))
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CROSSREFS
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Adjacent sequences: A071831 A071832 A071833 this_sequence A071835 A071836 A071837
Sequence in context: A105402 A083865 A117948 this_sequence A055196 A120624 A138873
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KEYWORD
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easy,nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Jun 08 2002
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