Problem 292: Pythagorean Polygons

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We shall define a pythagorean polygon to be a convex polygon with the following properties:there are at least three vertices,

no three vertices are aligned,

each vertex has integer coordinates,

each edge has integer length.For a given integer n, define P(n) as the number of distinct pythagorean polygons for which the perimeter is ≤ n.

Pythagorean polygons should be considered distinct as long as none is a translation of another.

You are given that P(4) = 1, P(30) = 3655 and P(60) = 891045. Find P(120).