This circuit is supplied as a hobby project. The 555 timer IC is connected for astable operation. The clock pulses are fed to the 4017 IC via the 10K resistor. The 4017 is a 10 stage counter; each of the outputs is connected to the appropriate LED. Some LEDs need to be on for more than one count. Therefore, we use diodes to avoid a short circuit situation between outputs. The capacitor and resistor on pin 15 of the 4017 are used to reset the counter to zero at initial power up.
You will also need, in addition to the parts list, a power source or supply of anywhere from 9 to 12 volts, less than 1 amp. The parts are readily available at Radio Shack or electronics hobby stores. The final finished product is shown below the parts list. You might also wish to see our Astable 555 Square Wave Calculator.