An addition chain for a number is a sequence , such that each member after is the sum of two earlier (not necessarily distinct) ones. The number is called the length of the addition chain. For example,

is an addition chain for 14 of length (Guy 1994).

More things to try:

Weisstein, Eric W. "Addition Chain." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/AdditionChain.html