Genuine Hp TPC-LA581 charger has 65w of power and outputs at 19.5v 3.33a which supports all the 18.5v 3.5a ac adapters also as they both charge via the older larger connector barrel which is 7.4mm outside diameter and 5mm inside diameter and both are 65w.

Genuine Hp TPC-LA581 charger specification:
Part number: TPC-LA581
Power: 65w
Output: 18.5v 3.5a / 19.5v 3.33a
Input: 100-240v
Pin tip size & type: Large 7.4*5mm barrel with centre pin
Outside diameter 7.4mm
Inside diameter: 5mm