Wolfram Alpha:

```Ordinary Annuity
----------------
A series of equal payments made at the END of each period over a
fixed amount of time.

----------------- (1 + r)1
|       ---------- (1 + r)2
|      |       --- (1 + r)3
|      |      |
v      v      v
+------+------+------+------+
0      1      2      3
|      |      |
1/(1 + r)1 <----      |      |
1/(1 + r)2 <----------       |
1/(1 + r)3 <-----------------

PV of ordinary annuity = C * {1 - (1 + i)-n}
-----------------
i

FV of ordinary annuity = C * {(1 + i)n - 1}
-----------------
i

i = interest rate
C = cash flow per period
n = number of payments

Annuity Due
-----------
A series of equal payments made at the BEGINNING of each period
over a fixed amount of time.

----------------- (1 + r)1
|       ---------- (1 + r)2
|      |       --- (1 + r)3
|      |      |
v      v      v
+------+------+------+
0      1      2      3
|      |      |
1/(1 + r)1 <----      |      |
1/(1 + r)2 <----------       |
1/(1 + r)3 <-----------------

PV of annuity due = C * {1 - (1 + i)-n} * (1 + i)
-----------------------------
i

FV of annuity due  = C * {(1 + i)n - 1} * (1 + i)
----------------------------
i ```