A group of chemists from Colombia performing experiments on a new medicine for a deadly disease, which was spread by some criminals in India. The group includes Robin, Lucas, More, Ramachandra and Li. They are staying in an area , each having their own cabin. Ramachandra is a senior scientist among them and he is also a mathematician. Robin is also a mathematician. They periodically testing the effectiveness of the medicine and its results. Ramachandra has a threat from the criminals who have spread that disease, because he knows everything about the medicine. So he cleverly and secretly kept all the documents related to the medicine in one of his colleagues cabin and gave all other scientists a paper containing a message “Medical Documents” and some numbers. He told them “keep it as a secret”. They couldn’t understand what the numbers are.

On one day, the criminals have attacked Ramachandra and cut his throat, searched for the documents and they have not found them. So they lit fire to all the cabins to burnt the proof of the medicine. All other scientists escaped from their cabins and heard shoutings of Ramachandra. All other scientists visited Ramachandra’s cabin. Before he died, he gave a SELFie stick to his colleagues. It is the SELFie stick used by the scientists to take selfies during their experiments. The scientists have no time to search all the cabins, because they are burning. They have a piece of paper and SELFie stick. So how can they find the correct cabin?

Clues are:

SELFie stick


Paper containing the following information:


8, 11, 6, 3, 9, 4

  • $\begingroup$ Any pictures supporting your story? $\endgroup$
    – Matsmath
    Sep 12, 2016 at 12:21
  • $\begingroup$ Use the story and gather important words... $\endgroup$
    – KSR
    Sep 12, 2016 at 12:22
  • $\begingroup$ Ramachandra is a (very strange for me) name made with 11 letters. I thought that the key of the code was the name of the person who gave the stick, Ramachandra himSELF. I tried some substitution but nothing has sense. Very interesting $\endgroup$
    – marcoresk
    Sep 12, 2016 at 15:53
  • $\begingroup$ Ramachandra name is important.. but not that way $\endgroup$
    – KSR
    Sep 12, 2016 at 16:21
  • $\begingroup$ From your story I believe the person whose cabin has the documents would know that theirs was the right cabin, so do they even need to work out what the paper says? $\endgroup$
    – yuzuki
    Sep 13, 2016 at 5:05

1 Answer 1


There are two hints to the meaning of the numbers on the paper:

The sceintists are from Colombia and there is this ominous selfie stick with self in all caps.

This leads us to ...

Self numbers or Colombian numbers: These are numbers that cannot be written sa m + sum of digits of m for any m. (For example, the non-Colombian number 6 can be written as 3 + 3; 11 can be written as 10 + 1 + 0; 23 can be written as 16 + 1 + 6 and so on.)

Anyway, let's just use that convenient OEIS page and replace each number n on the scrap of paper with the nth Colombian number and we get:

42, 75, 20, 5, 53, 7

Now, ...

... these guys are scientists, and they are "periodically testing" a type of medicine. That certainly rings a bell for Mendeleev's dog: Replace the numbers with the respective chemical element from the periodic table:

Mo, Re, Ca, B, I, N

or, properly spaced: More cabin. So the documents are in the cabin of our colleague More.


This answer is really a wrap up of the results that Maria Deleva and Arka Karmakar have found out:

Maria spotted the connection with chemical elements and Arka found out that in an earlier version of the question the Colombian numbers appear verbatim.

So a big tip of hat to them.


I really worked backwards from the solution already very probably found by Arka:

Since the actual numbers were buried in the edit history, I and searched for a sequence that went ✻, ✻, 5, 7, ✻, 20, ✻, 42, 53, ✻, 75, ...

When that search turned up a sequence of Self numbers, which can also be called Colombian numbers I knew I had it, but I hadn't heard of those numbers before.


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