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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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That is very good, you kept the dominant terms.

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
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Exactly. They seem to do the job good enough. I will try getting the closed form analitically today.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 89,150

Uh wait. That is the analytical answer up there. So you will looking for a shorter one?

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
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You didn't get it by analityc methods. You used M's FindSequenceFunction command. I want to see if I can get the answer analitically.

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Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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All you provided me was with your original algorithm. I had to use the sequence. And why not just try induction and prove the a_n is correct?

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
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Do you think there is a nicer reccurence for the sequence?

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Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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Maybe. The weirdest thing is that sequences can have more than one difference equation.

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
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I have the difference equation. It's a[n+4]-4a[n+2]-a[n]+4a[n-2]=0. Don't ask how I got it!

*Last edited by anonimnystefy (2013-04-17 04:41:07)*

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 89,150

I am going to ask just that.

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
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It is a bit tough to explain. I played a little bit of spot-the-pattern...

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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The solution to that will probably be longer than the other one.

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
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I think you will get the same solution.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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Possibly, or the trigonometric terms will be replaced by (-1)^n or something like that.

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
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The trigonometric terms will be replaced by i^n and (-i)^n.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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Yes, that is possible too but I would not exactly call that simpler.

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
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True. But the reduced form looks really nice, though!

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**bobbym****Administrator**- From: Bumpkinland
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It is an asymptotic form yes? It is supposed to be shorter and easier to compute.

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
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Yes. It looks much much prettier than the nasty exact one.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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But you possibly missed the forest for the trees.

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
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How?

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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It appears there might be a pattern worth investigating that is much simpler. It may not hold but it is worth a look. You have to get out of the box axiomatic math puts you in. It is small, dark and has little air.

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
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Which pattern? In the binary representation? That is the one I used to get the difference equation.

Hm, could you do asymptotic_a[n]-a[n] for me?

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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One question at a time can be investigated well. This one is more important.

Which pattern? In the binary representation?

No, not that one. Look below, is there anything cooking?

**In mathematics, you don't understand things. You just get used to them.**

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
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Well, they approach 1. That is why my formula is an asymptotic one. I also notice that every fourth term repeats two terms later. I do not notice anything else.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
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Yes, the differences between the asymptotic form and the actual answer follow a pattern.

1,3, then 1,1,1,3...

This suggests 2 recurrences and just adding the appropriate constant. Now you would have a short exact answer.

**In mathematics, you don't understand things. You just get used to them.**

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