A blue LED has a typical voltage drop of about 3V. Thus if they run off of 4.5V, the must be in parallel with a resistor in series with each bulb. (For 20mA nominal current and a 57Ω series resistor, this would indicate the voltage drop of each LED is 3.36V.)
You can only put three of them in series (with a suitable current limit resistor) for a 12-14V supply. You could put seven sets in parallel: Six sets of three in series plus one set of two in series to get 20 LEDs total.
For 20mA typical operating current you would need a ≈170 ohm resistor (3 each) in series with each string of three. You would need a ≈340 ohm resistor in series with the one string of two.