  The Born-Oppenheimer potential for the $^1\Sigma_g^+$ state of H$_2$ is
obtained in the range of 0.1 -- 20 au, using analytic formulas and recursion
relations for two-center two-electron integrals with exponential functions. For
small distances James-Coolidge basis is used, while for large distances the
Heitler-London functions with arbitrary polynomial in electron variables. In
the whole range of internuclear distance about $10^{-15}$ precision is
achieved, as an example at the equilibrium distance $r=1.4011$ au the
Born-Oppenheimer potential amounts to $-1.174\,475\,931\,400\,216\,7(3)$.
Results for the exchange energy verify the formula of Herring and Flicker
[Phys. Rev. {\bf 134}, A362 (1964)] for the large internuclear distance
asymptotics. The presented analytic approach to Slater integrals opens a window
for the high precision calculations in an arbitrary diatomic molecule.

Chemical Physics