A006339

[Graeme McRae]

Start with A004018.  See the formula listed there.  Pythagorean triangles 
can't have zero-length sides, so subtract 4 to eliminate the 4 points on the 
axes.  Triangles can't have negative length sides, so divide that number by 
4 to get the solutions in the first quadrant only.  In your case, 1105^2 = 
5^2 13^2 17^2, so the number of lattice points is 4(3)(3)(3).  The number of 
triangles is (4(3)(3)(3)-4)/4 = 13
--Graeme

----- Original Message ----- 
From: "David Wilson" <davidwwilson at comcast.net>
To: "Sequence Fans" <seqfan at ext.jussieu.fr>
Sent: Monday, January 16, 2006 11:22 AM
Subject: Re: A006339


> Can someone tell me how to compute, say, the number of distinct 
> Pythagorean triangles with hypotenuse 1105?
>
>