An entry into the 20th fortnightly topic challenge.
If a number conforms to a certain rule, I call it a Frightful Number™. Use the following examples to find the rule:
Here is a CSV:
Frightful Numbers™,Non-Frightful Numbers™ 15,23 427,487 729,512 2016,6210 13579,24680 492717,638424 1837591,4295354 43728161,15594260 1010101010,1001001001 1738629405,7293548016 46819275183,62571139572 92729092729,72627472627 7070707070707,4141414141414
The puzzle relies on the series' inbuilt assumption, that each number can be tested for whether it is a Frightful Number™ on its own. In particular, a number's relationship to other numbers in the sequence is irrelevant.
These are not the only examples of Frightful Numbers™ (or non-Frightful Numbers™), more can be found.
The title of the puzzle is a synonym for the required property - this is to ensure that it isn't too easy (it would be if I gave you the word)
The whole number being Frightful™ is a property of its parts
Frightful Numbers™ and Not Frightful Numbers™ have a real-world application.
Your challenge is (assuming you have found an answer to the main puzzle) to find what this could be ... It's not too hard to think of if you have the correct answer.
I think I might have missed the Halloween boat on this one... Oh well...
Here's hoping I don't make another silly mistake like last time!