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 (12)

  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…

  12. #12 Name
    Or 20
    26. März 2019

    20 22 20 15 20 1

    I added first set to get 42, subtracting it from the next set of 35, gave a 7…I applied the sequence again to see if a pattern emerged, and instead of a 7, I got double(or rather current num value added to previous) 14 value, so I figured expected value would be +7 more, or 21.

    So 42-35=7 35-21=14 21-X=21

    Not sure if that’s correct, or close, but like someone else said, there are likely many answers. In this case we formed a reasonable way to carry on the progressions given the value set so following our pattern we get 21 as our first set….and we also get 7+7+7 (21) as the expected value, but lacking the next set of numbers we would use to continue the pattern, my example stopped at 21 minus an expected value of X, or set of X…Lacking data, looks ok…cause x is ok with being X, with or without “sets” that it may or may not ever need or be using. Which means we may also conclude that the sign as well could end up not as 21-x=21….which assumes the negative is confined to stay with X, but it looks as if the abs value could jump logically to the first sets additive value being negative in place of the value X, especially since the value X is passing what could be the value X in any given direction of movement….

    Or if you wanna be a smartarse…

    5 vars, divided into 2 sets of 3 vars….sooo one set
    20 22 20 next set 15 20 1

    Add either the 2 smallest values together or the first and last values…….If the values when added are greater than the middle value say 20+20 > 22…then either add the values and subtract the middle var OR DIVIDE(The var not first or last from either side approaching the problem) So 40-22=18 Same as dividing….1.818181 OR since you had to subtract…..now double the value….and you’d get 36. Next set add first last, if value is larger subtract middle…..if value is less than middle…ADD middle to first last variables….so 16+20….or 36….and so on, etc:) You can also try reducing them first and running into what looks like PI

    4 11 4 3 4 1…..Or 200, 60, and 4! But that’s not a time, times and “half a time”………Everyone knows that’s 60, 1, and ¼. !!

    Haha and if it’s TVTOTA That means V should be 22….But V is equal to 1 5 which looks like 15!! *Head explodes*