The 4-loop sunrise graph with two massless lines, two lines of equal
mass M and a line of mass m, for external invariant timelike and
equal to m^2 is considered. We write differential equations
in x=m/M for the Master Integrals of the problem, which we Laurent-expand
in the regularizing continuous dimension d around d=4, and then
solve exactly in x up to order (d-4)^3 included;
the result is expressed in terms of Harmonic PolyLogarithms of
argument x and maximum weight 7. As a by product,
we obtain the x=1 value, expected to be relevant in QED 4-loop
static quantities like the electron (g-2). The analytic results
were checked by an independent precise numerical calculation
