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Mar 4, 2010 at 5:46 comment added Douglas S. Stones Do you actually mean they never have closed forms (i.e. can it be proved that a "closed form" (defined in some concrete manner) doesn't exist in some cases?), or that we're currently unable to find them (i.e. it is possible that someone in the future could find one)?
Jan 21, 2010 at 14:33 comment added Kevin Buzzard [Or x_{n+1}=cx_n^2, he said, pedantically]
Jan 21, 2010 at 14:02 answer added Julián Aguirre timeline score: 1
Jan 21, 2010 at 4:00 comment added Qiaochu Yuan In fact, to my knowledge the only quadratic recurrence which has anything like a closed form is (anything that reduces to) x_{n+1} = 2x_n^2 - 1 because of the cosine double-angle formula.
Jan 21, 2010 at 3:55 comment added Gjergji Zaimi mathoverflow.net/questions/9660/…
Jan 21, 2010 at 3:50 comment added Jason Knight Seems like I'm out of luck. I just compared the function in question with logistic maps (the similarity is striking). No wonder I was butting my head against a wall.
Jan 21, 2010 at 3:39 comment added Zev Chonoles Qiaochu is right. Whatever general results there are for nonlinear recurrences, they should be in here: books.google.com/… I own this book myself, but have only studied the parts of it relevant to linear recurrences, so I can't direct you to anything specific.
Jan 21, 2010 at 3:29 comment added Jason Knight I changed the title as suggested.
Jan 21, 2010 at 3:28 comment added Qiaochu Yuan Generally speaking, nonlinear recurrences almost never have closed forms.
Jan 21, 2010 at 3:28 history edited Jason Knight CC BY-SA 2.5
edited title; edited title
Jan 21, 2010 at 3:08 comment added Zev Chonoles I think you may want to retitle this something like "Closed form for a nonlinear recurrence sequence?"
Jan 21, 2010 at 2:26 history asked Jason Knight CC BY-SA 2.5