The "precession" per time T =
3 * (G * M)^(3/2) * T / (c^2 * a^(5/2) * (1 - e^2))
Notice that Pi is absent.
This formula applies to elliptical orbits, "a" being
their semi-major axis and "e" their eccentricity.
Notice also that "e" can be zero.
The result is a dimensionless number, thus not an angle.
By multiplying that result by (180/Pi)*3600, one gets
for Mercury
   with T = 1 sec:       1.362 * 10^-8 "something"
   with T = 3.155815E+09 sec (1 century):  42.99 "something"

Hence, the so-called GR extra-precession of
42.99 arc-sec per century is false, because it is
in fact 42.99 "something", which is not an angle.

Moreover, one gets 41.168 "something" when e=0 !

GR seems to be a hoax !

Marcel Luttgens