# series 0, 6, 13, 20, 27

I'm working with days of the week and need to generate a series thats $n*7-1$ except for where $n=1$ where it should be $0$.

So the series I'm after is $0,6,13,20,27$

I can't figure out a formula for this series though!

Any help would be appreciated!

Many thanks

• Shouldn't it be $0,6,13,20,27$? – kingW3 May 26 '18 at 13:21

$$f(n) = \begin{cases} 7n -1 & n \ne 0 \\ 0 & n= 0 \end{cases}$$
$a_n=7n-1+\delta_{0,n}$
Note we start with $n=0$.