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Numbers that can be written as (a^2-1)(b^2-1) in four or more distinct ways.
4

%I #7 Sep 25 2013 02:19:38

%S 241920,1048320,10200960,25724160,37255680,93139200,123963840,

%T 245044800,588107520,819786240,1407893760,1871251200,3758169600,

%U 5886558720,8553283200,10783342080,13470367680,19769460480,30791819520,40446806400

%N Numbers that can be written as (a^2-1)(b^2-1) in four or more distinct ways.

%C Subsequence of A134856. Contains A134858 as a subsequence.

%H MathPages, <a href="http://www.mathpages.com/home/kmath275.htm">Numbers Expressible As (a^2-1)(b^2-1)</a>.

%e 241920 = (4^2-1)(127^2-1) = (7^2-1)(71^2-1) = (9^2-1)(55^2-1) = (17^2-1)(29^2-1).

%Y Cf. A134856, A134858.

%Y Cf. A057535, A063066, A063067, A063068.

%K easy,nonn

%O 1,1

%A _Herman Beeksma_, Nov 13 2007