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).

Guy, R. K. Addition Chains. Brauer Chains. Hansen Chains.'' §C6 in Unsolved Problems in Number Theory, 2nd ed. New York: Springer-Verlag, pp. 111-113, 1994.