
Originally Posted by
Bruno J.
We have the identity
which shows that it's impossible for the sequence
)
to be eventually constantly equal to -1. If it is eventually constantly equal to 1, let

be the greatest integer such that
=-1)
. Then by hypothesis
^2-2)=1)
and then
f((s+1)^2-2)=f\left((s^2+s-2)^2-2\right))
, contradicting the choice of

.
nice!

just note that before choosing the greatest integer

with
=-1)
you should mention that basically the set
=-1 \})
is non-empty.
this, of course, is trivial in our case because

but it becomes absolutely non-trivial if we replace

with an arbitrary non-zero integer
finally the identity you used can be extended. in general we have:
You always have nice problems, NonCommLion.
thanks! i like my new user name: NCL! it could also stand for Normal CLosure!
Where do you get them from?
here and there!