Lm317 input connected to output?
I can think of two reasons for a 3k bypass resistor:


To provide a discharge path for the capacitors when the power is switched off.
To reduce the power dissipation in the LM317.


With a 36 V supply the maximum current through the 3k resistor for a 15 V load would be \$ I = \frac {V}{R} = \frac {36 - 15}{3k} = 7 \ \mathrm {mA} \$.
If the load draws more than 7 mA then the output voltage from the resistor alone will be &lt; 15 V. 

With the addition of the LM317 it can now pass the remainder of the current required to bring \$ V_{OUT} \$ back up to 15 V.

Power dissipation in the 3k resistor will be \$ P = VI = 21 \times 7m = 147 \ \mathrm{mW} \$. This seems low relative to the power handling capability of the LM317 so I suspect that reason 2 is not the right one.