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Search: id:A027687
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| A027687 |
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Quadruply-perfect numbers: sum of divisors of n is 4n. |
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+0
13
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| 30240, 32760, 2178540, 23569920, 45532800, 142990848, 1379454720, 43861478400, 66433720320
(list; graph; listen)
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OFFSET
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1,1
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REFERENCES
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R. K. Guy, Unsolved Problems in Number Theory, B2.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..36 (complete sequence)
Walter Nissen, Abundancy : Some Resources
Achim Flammenkamp, The Multiply Perfect Numbers Page
Fred Helenius, Link to Glossary and Lists
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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MATHEMATICA
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AbundantQ[n_]:=DivisorSigma[1, n]==4*n; a={}; Do[If[AbundantQ[n], AppendTo[a, n]], {n, 10^6}]; a [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Aug 16 2008]
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CROSSREFS
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Cf. A007539, A000396, A005820, A046060, A046061.
Sequence in context: A104877 A027665 A113286 this_sequence A109485 A156429 A134118
Adjacent sequences: A027684 A027685 A027686 this_sequence A027688 A027689 A027690
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KEYWORD
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nonn,fini
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AUTHOR
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Jean-Yves Perrier (nperrj(AT)ascom.ch)
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EXTENSIONS
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4 more terms from Labos E. (labos(AT)ana.sote.hu)
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