We have lots of challenges tagged sequence. What types of sequences make for interesting golf challenges? How can we assess whether a given sequence is worth writing a challenge about?
I understand that we need both easy and difficult challenges (for people with different ability levels in their chosen language(s), and for people with different amounts of free time), so this won't just be about that.
What factors are there to take into consideration when writing a sequence golf challenge?
I often see that questions which have multiple ways of being solved are more interesting than challenges which have only one exact way to approach the problem. If that's the case, it is just a contest of who has the best built-ins. When there are multiple approaches, it's also quite a puzzle of finding out which approach is better for your submission.
This is probably a corollary of Adnan's answer, but even with sequences that have many definitions and approaches there is often a simple closed form solution that a) completely sidesteps the interesting background of a sequence and b) is the only viable golfing option. Always try to make sure that closed form solutions are either hard to come up with or sufficiently complicated that they don't dominate the challenge (e.g. by checking the Formula section on OEIS).
(phi^n - (1-phi)^n)/sqrt(5) is much simpler and often shorter than the iterative or recursive computation methods (floating-point nonsense aside).
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This probably applies to all challenges. I found this out after posting some sequence-challenges, but the easier it is to understand the challenge, the more interested people are. If you come up with a very difficult challenge which require a lot of mathematical knowledge, people are less likely to submit an answer.
Also important, don't make it too easy. Trivial challenges are not encouraged to be posted, and would probably lead to 3-byte answers, etc.