a(5) = 71831760 is area of 5 Pythagorean triangles: 2415-59488-59537, 2640-54418-54482, 5070-28336-28786, 7280-19734-21034, 10010-14352-17498
The area of 7280-19734-21034 is (2*13)^2*the area of 280-759-809.
The area of 10010-14352-17498 is (2*13)^2*the area of 385-552-673.
These triangles have the same area as the triangles I get by solving p^2-p*q+q^2=r^2. r=169, p=15, q=176, (q-p)=161 Area=r*p*q*(q-p)
q=176 and r=169 gives 2415-59488-59537;
r=169 and q-p=161 gives 2640-54418-54482;
r=169 and p=15 gives 5070-28336-28786. (End)
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