(The power of the) Ellipsis
The next three terms in the following sequence:
3,3,10,11,11,18,10,10,17, …
are …….
either 18, 18, 25, or, if you are a little more modern, then 10, 10, 17.
The reason is that the numbers represent the number of letters in the powers of ten:
One, Ten, One Hundred, One Thousand, Ten Thousand, One Hundred Thousand, One Million, Ten Million, One Hundred Million,
followed by One Thousand Million, Ten Thousand Million, One Hundred Thousand Million
OR
One Billion, Ten Billion, One Hundred Billion.
How did you get on? I don’t think anyone gave us the short scale version of the answer 10, 10, 17, but we got quite a few who nailed it with 18, 18, 25.