Help me sub-divide a time signature
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.+
$*
1
RL
^(.+)RL\1$
$1R¶L$1
^(.+)\1$
$1
(.)(..?)(?!.\b)
$1$.2$*.


Try it online! Link includes test cases. Explanation:

.+
$*


Convert the input to unary.

1
RL


Alternate between hands.

^(.+)RL\1$
$1R¶L$1


If there are an odd number of beats then divide the output in the middle.

^(.+)\1$
$1


But if there are an even number of beats then just use one copy.

(.)(..?)(?!.\b)
$1$.2$*.


Try to match groups of three beats, but without leaving a lone beat at the end, and replace the offbeats with .s.