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A063893
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Numbers n such that sum of proper divisors or aliquot parts of n^2 is a square.
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0
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OFFSET
| 1,2
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REFERENCES
| A. H. Beiler, Recreations in the Theory of Numbers, Dover, NY, 1964, p. 10.
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EXAMPLE
| a(3)=49 because 49^2=2401 and sum of aliquot divisors of 2401: 1+7+49+343=400=20^2.
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PROG
| (PARI) s(n)=sigma(n)-n; for(n=1, 10^8, if(issquare(s(n^2)), print(n)))
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CROSSREFS
| Cf. A008847, A001065.
Sequence in context: A180602 A086459 A203700 * A145572 A012857 A034201
Adjacent sequences: A063890 A063891 A063892 * A063894 A063895 A063896
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KEYWORD
| hard,nice,nonn
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AUTHOR
| Jason Earls (zevi_35711(AT)yahoo.com), Aug 29 2001
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EXTENSIONS
| a(6) from Naohiro Nomoto (n_nomoto(AT)yabumi.com), Jun 06 2002
a(7) from Giovanni Resta (g.resta(AT)iit.cnr.it), Jan 31 2012
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