What is missing from this sequence?


Source: GCHQ Puzzle book

  • 2
    $\begingroup$ Nice puzzle... curious to see some answers. I'm stumped! $\endgroup$
    – grinch
    Sep 13, 2018 at 18:52

1 Answer 1


My answer is:



The word sequence given contains in order the 12th (Mu), 13th (Nu), 14th (Xi), and 16th (Pi) letters of the Greek alphabet reversed with an added "S". The missing Greek letter in the order is the 15th letter of the alphabet (Omicron). Following the same naming convention gives you SNORCIMO:

Mu = SUM
Nu = SUN
Xi = SIX
Omicron = SNORCIMO
Pi = SIP

  • 1
    $\begingroup$ Very nicely done! How did you spot it? $\endgroup$
    – Simd
    Sep 13, 2018 at 21:22
  • 3
    $\begingroup$ Well, I was trying to find a pattern for a while. When nothing was working I flipped the words backwards and the Greek letter just popped out at me! Great puzzle, I had a lot of fun even though it drove me crazy for a bit 😊 $\endgroup$ Sep 13, 2018 at 21:29
  • $\begingroup$ Sorry, it's not a word. $\endgroup$ Jun 25, 2020 at 0:16

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