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Least value of x*y giving Max ( sigma(x*y) : 1<=x<=n, 1<=y<=n ).
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%I #12 Mar 31 2012 10:31:16

%S 1,4,9,16,20,36,42,64,72,90,90,144,144,168,210,240,240,324,324,360,

%T 420,420,420,576,600,600,600,756,756,840,840,960,960,960,960,1260,

%U 1260,1260,1260,1560,1560,1680,1680,1680,1980,1980,1980,2160,2160,2400,2400

%N Least value of x*y giving Max ( sigma(x*y) : 1<=x<=n, 1<=y<=n ).

%C Value is unique by this definition up to a(103) = 9900. To go beyond this number, we could define the sequence in terms of "smallest value of x*y" or "largest value of x*y". We choose smallest here.

%e a(5) = 4 * 5 = 20; sigma(20) = 42

%Y Cf. A074963, A074964.

%K nonn

%O 1,2

%A _Stewart Gordon_, Sep 26 2011