perhaps voltage regulation is not needed and the set of LEDs would drop Vf*n across themselves.
the LM317 would only waste power as Vdiff * Iload as regulated by itself being a current regulator.
IMHO,
if a voltage regulation is foreseen like 48V battery and 30V drop across LEDs
then another front end lm317 could be placed as voltage regulator just to share the difference
input say 48, 1st stage out could be 36, and second stage would pump a predefined current.