Normally, governments have pension program, yet no 401K match.
Only a handful of companies offer both pension and 401 K match.
Regarding your case:
Assuming that your starting salary is 100K, your salary after 20 years of service will be from 180 to 260K if the annual salary increase is assumed to from 3 to 5 percent.
Annual income from pension program is generally proportional to the num. of service years.
for a 20 years of service, the rate could be around 0.4 to 0.5.
Thus, your retirement form pension will be
180 K to 260 K multiplied by 0.4 to 0.5. in other words, 72 K to 130 K.