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Numbers x,y,z such that UnitarySigma(x) = UnitarySigma(y) = UnitarySigma(z) = 3*(x*y*z)^(1/2)/(- x^(1/2) + 8*y^(1/2) - 5*z^(1/2)), z<=y<=x; sequence gives x.
4

%I #14 Jan 24 2019 04:50:55

%S 2,20,24,360,816,1056,12240,15840,29120,181632,337977,2724480,

%T 93358848,1400382720

%N Numbers x,y,z such that UnitarySigma(x) = UnitarySigma(y) = UnitarySigma(z) = 3*(x*y*z)^(1/2)/(- x^(1/2) + 8*y^(1/2) - 5*z^(1/2)), z<=y<=x; sequence gives x.

%C a(11) is the smallest term for x!=y, y!=z, x!=z.

%C If x=y=z then we get multiply unitary perfect numbers such that UnitarySigma(x)=3x/2.

%e Factorization of a(11) : 17*3^2*47^2.

%Y Cf. A034448, A144673, A144674 (these entries all differ at a(11)).

%K nonn,more

%O 1,1

%A _Yasutoshi Kohmoto_, Feb 02 2009