Characteristic sequence

Characteristic sequence

In mathematics, the characteristic sequence of a given sequence s is a sequence of 1's and 0's which tells which elements of s are in some set.

Given two sets A \subseteq B and a sequence s = \langle s_n : n \in \mathbb{N}\rangle of elements of B, the characteristic sequence of s is the sequence \langle c_n : n \in \mathbb{N}\rangle defined so that cn = 1 if and only if s_n \in A:


c_n = 
\begin{cases}
0 &  s_n \not \in A, \\
1 &  s_n \in A.
\end{cases}