A063831 Sum of cubes of divisors is a square.
1, 2, 345, 690, 47196, 46248900, 53262468, 71315748, 140553735, 188194335, 215515727, 281107470, 288564647, 292978595, 310129096, 376388670, 431031454, 577129294, 585957190, 1474108335, 2133051720, 2489605188, 2948216670, 3270679304, 4043104611, 5142743032
Offset: 1
Keywords
Examples
345 is in the sequence since sigma_3(345) = 6552^2 is a square.
Programs
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Mathematica
Select[Range[10^5], IntegerQ[ Sqrt[ DivisorSigma[3,#] ] ] &] (* Amiram Eldar, Dec 06 2018 *)
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PARI
for(n=1,10^5, if(issquare(sigma(n,3)),print1(n, ", ")))
Extensions
More terms from Thomas Baruchel, Oct 20 2003
More terms from Sean A. Irvine, Sep 24 2009
a(24)-a(26) from Amiram Eldar, Dec 06 2018