HP HP-65 - Page 67

Sample Case: Sum of First n Digits. Calculate the sum of 1 4 2
+ 3 4 ... -+ n where n is in the x-register at the beginning.
Switch to W/PRGM.
Press [ to clear memory.
Key in the following steps.
Keys Comments
D
STO Preset n in R..
| (sx Clear stack.
] Beginning of repeat segment.
RCL Recall r; to X.
Add to previous sum.
&+
B
Decrement
rs
(rs
—
1— Ry) and test for zero.
Repeat if rs is not zero.
L0 Stop after nth iteration.
Calculating the Function
Switch to RUN.
Press See Displayed Comment
5 B - Sumof1 424 ...45.
20 @ 210.00 Sumof 1 -2 ... 20.
25 8 Sumof 1 42 +...+25.