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Search: id:A008848
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| A008848 |
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Squares whose sum of divisors is a square. |
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+0
3
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| 1, 81, 400, 32400, 1705636, 3648100, 138156516, 295496100, 1055340196, 1476326929, 2263475776, 2323432804, 2592846400, 2661528100, 7036525456, 10994571025, 17604513124, 39415749156, 61436066769, 85482555876, 90526367376, 97577515876, 98551417041
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Solutions to sigma[x^2]=square of odd number. - Labos E. (labos(AT)ana.sote.hu), Aug 22 2002
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REFERENCES
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A. H. Beiler, Recreations in the Theory of Numbers, Dover, NY, 1964, p. 10.
I. Kaplansky, The challenges of Fermat, Wallis and Ozanam (and several related challenges): II. Fermat's second challenge, Preprint, 2002.
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EXAMPLE
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n=32400: sigma[32400]=116281=341^2=121.961
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MATHEMATICA
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Do[s=DivisorSigma[1, n^2]; If[IntegerQ[Sqrt[s]]&&Mod[s, 2]==1, Print[n^2]], {n, 1, 10000000}] (Labos)
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CROSSREFS
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a(n) = A008847(n)^2.
Cf. A028982, A001248, A000203.
Sequence in context: A017498 A097025 A074387 this_sequence A017630 A128912 A076090
Adjacent sequences: A008845 A008846 A008847 this_sequence A008849 A008850 A008851
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KEYWORD
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nonn
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AUTHOR
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njas
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