Another exploration problem

An expedition party has to explore deep inside of a jungle. Each member can carry a pack of food that lasts the member exactly 2c2c days, and each member can walk one unit distance in cc days. For a party of nn members, let d(n)d(n) denote the distance from the base camp to the farthest point at least one member of the party can reach. We present a few values of d(n)d(n) and bounds on d(n)d(n). Several problems are posed.