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[Euler] Need clarification
November 21, 2011 at 2:25 pm
Please note that this is not a homework, I am not a student 
The problem description is here: http://projecteuler.net/problem=2
It is said "By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms."
Now, due to my really really bad english, should we:
1. SUM all EVEN fibonacci number until sequence just before 4000000 (which is 399999) ? or
2. SUM all EVEN fibonacci number which values is below 4000000 (which is 3524578) ?
* I think I cannot survive high-school in English country 
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RE: [Euler] Need clarification
November 21, 2011 at 2:59 pm
The problem suggests a finding of a sum of even terms of Fibonacci sequence:
S=2+8+34+... (+all even numbers less than 4000000)
This problem can be easily solved by using a general term formula for Fibonacci sequence and by using a formula for a sum of geometric progression.
By the way. Thank you for the problem. It will be a good task for my students.
The whole religion - it's a great trolling, beginning with "and prove that there is no God."
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RE: [Euler] Need clarification
November 21, 2011 at 3:10 pm
Thanks Bertran,
So the number would be:
0, 2, 8, 34, 144, 610, 2584, 10946, 46368, 196418, 832040, 3524578
and the SUM is: 4613732 ?
Am I correct? (just tell me am I correct or not )
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RE: [Euler] Need clarification
November 21, 2011 at 3:15 pm
This is a cheating. But anyway, your result is correct.
The whole religion - it's a great trolling, beginning with "and prove that there is no God."
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RE: [Euler] Need clarification
November 21, 2011 at 3:17 pm
Thanks Bertran, btw I input my answer to:
http://projecteuler.net/problem=2
And they said it is incorrect.
Either our understanding is wrong, or their understanding and other 150000 people is wrong
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RE: [Euler] Need clarification
November 21, 2011 at 3:31 pm
It is very strange. It is interesting to hear another persons and how they did understand this problem.
The whole religion - it's a great trolling, beginning with "and prove that there is no God."
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RE: [Euler] Need clarification
November 21, 2011 at 3:58 pm
Make sure there isn't any whitespace (tabs, spaces, etc) surrounding your answer. I can confirm that 4613732 is the correct answer, since I solved that problem years ago.
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RE: [Euler] Need clarification
November 21, 2011 at 4:49 pm
(November 21, 2011 at 2:59 pm)Bertran Wrote: This problem can be easily solved by using a general term formula for Fibonacci sequence and by using a formula for a sum of geometric progression.
Just out of curiosity, what are the relevant formulae? (Not a student, just a middle-aged guy that's been out of math of a long time)
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RE: [Euler] Need clarification
November 21, 2011 at 5:17 pm
(This post was last modified: November 21, 2011 at 5:18 pm by Bertran.)
(November 21, 2011 at 4:49 pm)Cthulhu Dreaming Wrote: Just out of curiosity, what are the relevant formulae? (Not a student, just a middle-aged guy that's been out of math of a long time) Of course, I'm talking about this formula for F_n.
The whole religion - it's a great trolling, beginning with "and prove that there is no God."
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RE: [Euler] Need clarification
November 21, 2011 at 5:28 pm
(November 21, 2011 at 5:17 pm)Bertran Wrote: (November 21, 2011 at 4:49 pm)Cthulhu Dreaming Wrote: Just out of curiosity, what are the relevant formulae? (Not a student, just a middle-aged guy that's been out of math of a long time) Of course, I'm talking about this formula for F_n.
Thanks. Interesting, yet (somewhat) incomprehensible, as my math education ended at high-school trigonometry. One of these days, I'll have to figure out that high falutin' math stuff.
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