prob75(N)=
{
	\\ call with -s 400000000
	perim = 0;
	r = 2;
	fib = listcreate(N);
	for (i = 1, N, listput(fib,0));
	while (r < N,
		v = r^2 / 2;
		fordiv(v, s,
			if (s <= sqrt(v),
				\\ this is Dickson's method to generate Pythagorean triples
				t = v / s;
				x = r + s;
				y = r + t;
				z = r + s + t;
				perim = x + y + z;
				if (perim <= N,
					listput(fib,fib[perim] + 1,perim);
				);
			,
				break;
			);
		);
		r += 2;
	);
	c = 0;
	for (i = 1, N,
		if (fib[i] == 1, c++);
	);
	print (c);
}