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