The very cool circuit is from here: http://engmousaalkaabi.blogspot.com/2016/01/81-led-chaser-using-double-ic-4017.html
Here are my few questions regarding it.
1, It has 18 transistors. are they really required for lighting up some small LEDs? I think 9 transistors should work.
2, It's about the 4017. When powering on and without a clock signal from 14, does Pin 3 (first output) goes HIGH or LOW? (according to this circuit, Pin 3 much go HIGH for it to work.)
3, what is 3.3k doing in this circuit?
4, last and my main question will be. Can I replace a 555 ic without a micro-controller such as a small attiny 95 and turn this array of leds into a clock? will the CD4017 fast enough for that? according to the datasheet, it has 2.5mhz clock input.