Random Blinking (Flashing) LED
We can using this circuit to make the LEDs blink in a random pattern according to the slight differences in the three Schmitt Trigger oscillators.
The CD4511 is BCD to 7 segment Driver, so the pattern of the led is actually the come from seven segment representation. Arrange the LEDs to be far from seven segment pattern if you want to avoid people analyze your circuit. The randomness is based on the frequency difference because the 22uF and 47k resistors that determine the frequency have at least 5% tolerance.