A127702 Least value of x*y giving Max ( sigma(x*y) : 1<=x<=n, 1<=y<=n ).

1, 4, 9, 16, 20, 36, 42, 64, 72, 90, 90, 144, 144, 168, 210, 240, 240, 324, 324, 360, 420, 420, 420, 576, 600, 600, 600, 756, 756, 840, 840, 960, 960, 960, 960, 1260, 1260, 1260, 1260, 1560, 1560, 1680, 1680, 1680, 1980, 1980, 1980, 2160, 2160, 2400, 2400

Offset: 1

Author

Stewart Gordon, Sep 26 2011

Keywords

• nonn

Comments

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.

Examples

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

Crossrefs

Cf. A074963, A074964.