Test 1
Write the function leibniz that takes an integer k and returns sum of the firth kth terms in Leibniz series as follows. More information about the Leibniz series can be found here.
$$ 1\,-\,{\frac {1}{3}}\,+\,{\frac {1}{5}}\,-\,{\frac {1}{7}}\,+\,{\frac {1}{9}}\,-\,\cdots \,=\,{\frac {\pi }{4}} $$
leibniz(1) -> 1
leibniz(3) -> 0.867