I'm working on a circuit with 21 outputs using 4017's, sequenced by a pushbutton. As the 'score' increments from output 20 to the 21st, I'd like to somehow activate a 555 (or similar) to rapidly clock the counters like a sequencer - to 'celebrate' reaching 21, until the counters are reset. I've got the basic circuit working pretty well - but can't get past square one the auto - sequencing part of the circuit. I thought I could use the 21st output to turn on a 555 to provide a clock input - not sure how to implement... Any ideas?