The sequence ($\displaystyle {f}_{{n}}$) is 4, 2, 6, 8, 14, 22, 36,
58, 94, 152, 246, 398, 644, 1042,
1686, 2728, 4414, 7142, 11556, 18698, 30254, ... The initial two values are $\displaystyle {f}_{{0}}={4}$ and $\displaystyle {f}_{{1}}={2}$. (Note, this indicates how the sequence is indexed.)

Let us take the value of $\displaystyle {n}={2}$. Compute the value for each of the following:
a.   $\displaystyle {f}_{{{n}+{1}}}$ =
b.   $\displaystyle {f}_{{{2}{n}}}$ =
c.   $\displaystyle {f}_{{{3}{n}-{2}}}$ =