Answer:
The n-th term of this sequence appears to be
3
n
−
1
,
n
≥
1
.
Explanation:
These are powers of
3
ordered from
3
0
=
1
to
3
a
(for an integer
a
≥
1
). However, the first convenient value for
n
is
1
, not
0
(imagine saying the 0th term of a sequence). Because of that, since the first term is actually
3
0
, we need to start from the first term (
n
=
1
) being
3
1
−
1
. The next is
3
2
−
1
,
3
3
−
1
...
3
n
−
1
.