Recursively, this sequence is given by
\(\begin{cases}a_1=-13\\a_n=a_{n-1}-4&\text{for }n>1\end{cases}\)
You can solve for the \(n\)th term explicitly:
\(a_n=a_{n-1}-4=a_{n-2}-2\times4=a_{n-3}-3\times4=\cdots=a_1-(n-1)\times4\)
So the explicit formula for this sequence would be
\(a_n=-13-4(n-1)=-4n-9\)
This means the 41st term is
\(a_{41}=-4(41-1)-9=-173\)
