To determine which of the given numbers is not part of the Fibonacci sequence, let's start by identifying the numbers in the Fibonacci sequence up to a reasonable range, considering the options provided.
The Fibonacci sequence starts with:
[tex]\[
a_1 = 1, \; a_2 = 1
\][/tex]
From this point, we can calculate the next numbers in the sequence as follows:
[tex]\[
\begin{align*}
a_3 &= a_2 + a_1 = 1 + 1 = 2, \\
a_4 &= a_3 + a_2 = 2 + 1 = 3, \\
a_5 &= a_4 + a_3 = 3 + 2 = 5, \\
a_6 &= a_5 + a_4 = 5 + 3 = 8, \\
a_7 &= a_6 + a_5 = 8 + 5 = 13, \\
a_8 &= a_7 + a_6 = 13 + 8 = 21, \\
a_9 &= a_8 + a_7 = 21 + 13 = 34.
\end{align*}
\][/tex]
At this point, we have the following Fibonacci numbers:
[tex]\[
1, 1, 2, 3, 5, 8, 13, 21, 34
\][/tex]
Now, compare the given options:
A. 13: This number is in the sequence.
B. 24: This number is not in the sequence.
C. 5: This number is in the sequence.
D. 34: This number is in the sequence.
Therefore, the number that is not found in the Fibonacci sequence is:
[tex]\[
\boxed{24}
\][/tex]
