I wanted to make a light flicker for
15 times using For Loop node […] and
it didn’t work.
- loops wait for no one and execute as fast as they can - this usually means a single frame, too fast to notice
- it’s an equivalent of toggling the light 16 times very, very quickly - but you only see the very last result
There are dozens ways to achieve the goal, here’s one:
Above, 8 Ons and 8 Offs or thereabout 
.5s delay