Example L$\mathrm{.}1\mathrm{.}2.$ Let's check the formula for $a_n$ above actually matches what we saw in Excel.

$(1)$ In column C $($labelled "Formula Check"$),$ we are going to directly calculate $a_n$ using our formula above. In $C2,$ we put $"=3^{**}A2+4"($remember$,$ column A is where wc are storing our index, so this matches the formula we just discussed$).$ As before, use autocomplete to fill in the rest of column C$.$

$(2)$ If you've done things correctly, Columns B and C should match.

Next, let's do a quick example of an arithmetic scries.