Puzzle Up 2015

[bromp]

Aufgabe #13

#13 is not hard.
Take all possible 6-letter codes, and add to each combination 7th letter
computed as sum of first 6 letters by modulo 7 (assuming A=0, ..., G=6).
So we have 7**6 codes.

Example in the text of the problem is quite strong hint

Looks easy, as you write it, and I had expected something like this, but I had the impression I was missing something. I have to think about this a bit...

Thanks a lot!