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Search: id:A107654
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| A107654 |
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Numbers n such that if sum of the proper divisors of n is equal to m then n=phi(m). |
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+0
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| 52416, 435456, 1713600, 6407424, 9067520, 62000640, 535392000
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Next term is greater than 65*10^6.
4*10^9 < a(8) <= 46367354880. [From Donovan Johnson (donovan.johnson(AT)yahoo.com), Oct 12 2008]
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EXAMPLE
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62000640 is in the sequence because sigma(62000640)-62000640=187545888 and phi(187545888)=62000640.
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MATHEMATICA
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Do[If[n == EulerPhi[DivisorSigma[1, n]-n], Print[n]], {n, 65000000}]
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CROSSREFS
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Cf. A107653.
Sequence in context: A152512 A147530 A003134 this_sequence A015359 A057851 A058326
Adjacent sequences: A107651 A107652 A107653 this_sequence A107655 A107656 A107657
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KEYWORD
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more,nonn
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AUTHOR
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Farideh Firoozbakht (mymontain(AT)yahoo.com), May 26 2005
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EXTENSIONS
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a(7) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Oct 12 2008
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