A few years ago, German late-night show host Stefan Raab presented a number puzzle in his show “TV total”. It involves cryptography and should be easy to solve for readers of this blog.

German readers certainly know the late-night TV show TV total hosted by Stefan Raab, which aired from 1999 to 2015. A few days ago, I happened to watch an excerpt from a 2013 TV total episode on YouTube. This episode shows an interview between Raab and Thomas Wolf, who is described as one of the nine most intelligent people in the world. Wolf’s IQ is nearly 200, so he belongs to the Giga Society, an exclusive super-smart club.

A few non-cryptographic puzzles

In order to test Thomas Wolf, Raab presents a number of challenges, most of which are about extending a sequence of numbers or other objects. The following screenshot shows an example:

The sequence shown here is 4, 11, 25, 53, ?. The missing item is 109, because each number is derived from its predecessor by doubling it and adding 3. Here’s another one:

Can you solve this puzzle yourself?


A cryptograpic puzzle

The last challenge presented in the interview between Raab and Wolf is cryptographic in nature (which can’t be seen at first view, but becomes clear if one knows the solution):

The sequence of numbers presented is 20, 22, 20, 15, 20, 1, ?. Can a reader solve this one? Knowing that the challenge has to do with cryptography makes things easier. If you find the solution, post it in the comment section. If not, watch the video or wait until somebody else has posted it.

Further reading: Revisited: Four unsolved crypto challenges of Germany’s federal intelligence service

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Kommentare (11)

  1. #1 Thomas
    15. Januar 2019


  2. #2 Gerry
    15. Januar 2019

    b) and 12

  3. #3 Laie
    15. Januar 2019


  4. #4 M
    16. Januar 2019

    I second #2

  5. #5 Jürgen Liebenstein
    Landshut, Germany
    16. Januar 2019

    4, 11, 25, 53, ?

    My way to the solution:
    4 + 7 (1*7) = 11
    11 + 14 (2*7) = 25
    25 + 28 (4*7) = 53
    53 + 56 (8*7) = 109

    That’s the problem with IQ-Tests, there are often alternate solutions, here with the same result. Which one is more intelligent.

    I had examples, where the test says my answer was false, but it had to be correct. IQ-Tests are arrogant, because they think they have the only existing solution.

    I am intelligent enough, that I will never create a test, because it is very thin ice.

  6. #6 Dominik Witte
    16. Januar 2019

    12 (th letter of the German alphabet)

  7. #7 noch'n Flo
    16. Januar 2019


    Mit der Nummer mit den Nummern war ich selber vor 24 Jahren mal im Fernsehen (“Aber Hallo!”, RTL). Hat mir damals 7’000 DM eingebracht.

  8. #8 David Allen Wilson
    16. Januar 2019

    I agree with “b”, and the obvious answer they want us to choose is “20”, but there simply isn’t a long enough number series…

  9. #9 Marcel
    16. Januar 2019


  10. #10 Laie
    16. Januar 2019

    a0=a2=a4=a6=a(n*2)=20, just a filler
    a1 -a3 = 22-15 = 7
    a3 -a5 = 15-1 = 7×2
    so, a6=20, a7 would be 1-(3×7) = -20

    “tvtotatG”. Maybe “TVTOTAL” = 21,7,12,25?

  11. #11 Christoph Schmid
    25. Januar 2019

    12 – das L, das Ganze heißt TV TOTAL und die 20 ist der Index des Bustabens T im Alphabet, die 1 steht für A usw.
    Das ist nicht mal eine Verschlüsselung…
    jede Zahl ist einfach die Position des jeweiligen Bustabens im Alphabet.
    Darum sind da 3 x 20 drin weil TV TOTAL eben soviele T enthält…