PCI in LTE is physical layer Cell Identifier. Its range is from 0-503 total Identities as 504. It is consist of Primary Sync signal and Secondary Sync signal.
PSS possible values can be 0,1,2 and SSS value can be 0-167
PCI can be calculated as PSS+3x SSS
for an examples
SSS=5
PSS=1
PCI = 1+ 3*5=16
Here is an good read about PCI from techplayon.