LEDs Series-Parallel OK?

[DarkMatter]

This works better then expected, although not great, due to the LED internal
resistance.

One is much better off placing an LED in series with a resistor.
Make several. Place them on a pair of rails that are fed by a
constant voltage source that is regulated.

VIOLA!

 

[John Fields]

Here is more, altho maybe we have "enough already!"
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This page taken from an HP Opto Electronics Division (OED)
publication by McGraw-Hill in 1977. These guys were real hot
shots & regularly beat everything to death.

It does show some LED die actually connected in parallel
without benefit of current sharing resistors.