Is this a bountied low-quality question? The remarks in the comments and answers prove that the question is non-trivial, but that doesn't make up for the lack of context?

I'm not sure if this is a good or bad question, but I think it may benifit from moving to a different SE site. (Sorry if this is outside of the wheelhose of CURED, but I don't know if there is a chat room for migrate sudgestions)

@user2628206 It is already a contextless question and should be closed

@TeresaLisbon Not enough context. The solution probably uses the recurrence relation correponding to the sequence.

@Peter Definitely, we'll let it hang around and close later, or we can flag immediately. What I've usually seen is that if the number (in this case 29 +\sqrt(21)) isn't a Pisot number (or a conjugate of one) then this kind of a question is best solved using a computer and/or finding modular patterns of very short period, which isn't the case as one answer evidences.

D

D2

D3.

D2: I meant to link the question, not an answer.

D1, D2, D3.

D4, D5, D6.

D7, D8, D9.

D10, D11, D12.

@user21820 D3 is fully open, no close votes.

@user21820 Let us know if you meant to link a different question??

@amWhy it was just reopened an hour ago. May be after user21820 posted the request.

@ArcticChar Thanks for the info. I should have checked the time-line!