luhn: Fix apophenia error slowing student progress
apophenia - noun
"the tendency to perceive a connection or meaningful pattern between unrelated or random things"
compare: pareidolia - noun
"to perceive a specific, often meaningful image in a random or ambiguous visual pattern"
Merriam Webster's
@@ -19,27 +19,27 @@ are disallowed.
## Example 1: valid credit card number
```text
-4539 1488 0343 6467
+4539 3195 0343 6467
```
The first step of the Luhn algorithm is to double every second digit,
starting from the right. We will be doubling
```text
-4_3_ 1_8_ 0_4_ 6_6_
+4_3_ 3_9_ 0_4_ 6_6_
```
If doubling the number results in a number greater than 9 then subtract 9
from the product. The results of our doubling:
```text
-8569 2478 0383 3437
+8569 6195 0383 3437
```
Then sum all of the digits:
```text
-8+5+6+9+2+4+7+8+0+3+8+3+3+4+3+7 = 80
+8+5+6+9+6+1+9+5+0+3+8+3+3+4+3+7 = 80
```
If the sum is evenly divisible by 10, then the number is valid. This number is valid!
