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A063893 Numbers n such that sum of proper divisors or aliquot parts of n^2 is a square. 0

%I

%S 1,3,49,35713,102851,949818597,1070640001,74145779101,138452510557,

%T 158236686397

%N Numbers n such that sum of proper divisors or aliquot parts of n^2 is a square.

%C Numbers 640606652893, 2814821518321, 9081196437853, 36236716613821 and 97748813502577 are also terms. - _Donovan Johnson_, Mar 31 2012

%D A. H. Beiler, Recreations in the Theory of Numbers, Dover, NY, 1964, p. 10.

%e a(3) = 49 because 49^2 = 2401 and sum of aliquot divisors of 2401: 1+7+49+343 = 400 = 20^2.

%o (PARI) s(n)=sigma(n)-n; for(n=1,10^8, if(issquare(s(n^2)),print(n)))

%Y Cf. A008847, A001065.

%K hard,nice,nonn

%O 1,2

%A _Jason Earls_, Aug 29 2001

%E a(6) from _Naohiro Nomoto_, Jun 06 2002

%E a(7) from _Giovanni Resta_, Jan 31 2012

%E a(8)-a(10) from _Donovan Johnson_, Mar 15 2012

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Last modified May 14 13:20 EDT 2021. Contains 343884 sequences. (Running on oeis4.)