Sprocket
P(n) = 1 - (1 - P(1))^n
khz your starter is a Chikorita, however you're not allowed to use it except as an HM slave (unless someone else gives you a starter, in which case disregard this).
Take a Pidgey. You must have 6 badges to evolve it to Pidgeotto, and 12 badges to evolve it to Pidgeot. It must solo Jasmine in Olivine City, and Brock in Pewter City.
Take a Pidgey. You must have 6 badges to evolve it to Pidgeotto, and 12 badges to evolve it to Pidgeot. It must solo Jasmine in Olivine City, and Brock in Pewter City.