The ground state energy 𝐸 0(𝜆) of 𝐻 𝜆 = − 𝑑 2 /𝑑𝑥 2 − 𝜆 𝑒 −𝑥2 is computed for small values of 𝜆 by means of an approximation of an integral operator in momentum space. Such an approximation leads to a transcendental ...