Lesko's portable terminal access is a holotape in Fallout 3. It can be found on Doctor Lesko's corpse and grants access to two terminals in his Marigold station research area.
Transcript
I've gotten the security lockout on my portable terminal functioning. How marvelous! The code right now is 314159. I must memorize this and discard this note as soon as possible.
Behind the scenes
The terminal access code is a reference to the mathematical symbol pi (3.14159).