Lucas Numbers and Generating Functions

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The discussion revolves around using generating functions to derive an explicit formula for the Lucas numbers, defined by the sequence 1, 3, 4, 7, 11, 18, where each number is the sum of the two preceding ones. The initial approach involves summing the Fibonacci numbers and adjusting the indices to relate them to the Lucas numbers. The key relation L_{n+1} = L_n + L_{n-1} is emphasized, suggesting that L_n can be expressed in terms of Fibonacci numbers as L_n = F_{n+1} + F_{n-1}. The conversation highlights the importance of applying initial conditions to finalize the formula. Overall, the thread provides insights into the mathematical relationship between Lucas and Fibonacci numbers through generating functions.
Johnny Numbers
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Here is my problem and my attempt at the answer. Any help or advice is highly appreciated.
Problem
With the famous sequence of Lucas numbers 1, 3, 4, 7, 11, 18... (Where each number is the sum of the last two and the first two are defined as 1 and 3.) use generating functions to find an explicit formula for the Lucas function.
Attempted Solution
We have
\sum_{j=1}^{n}F_jx^j
where Fj denotes the jth Fibonacci number and n is going to infinity. Then we add that to
\sum_{j=-1}^{n}F_jx^j^+^2
Where F-1 = -1 and F0 = 0

And that should get us a function of Lucas numbers right?:confused:
 
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The Lucas numbers satisfy the relation

L_{n+1} = L_n + L_{n-1}

Just set L_n = a^n and solve for a. Your generating function will be a linear combination of the two solutions. Apply your initial conditions ( L_1 and L_2) to determine the two arbitrary constants and you're done! :)
 
I should've been more specific, but we have to use the Fibonacci numbers to generate the Lucas numbers in this manner.

EDIT: I changed it up a little bit as well.
 
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In that case, it should be apparent that L_n = F_{n+1} + F_{n-1}
 
Ok so I believe that matches what I was intending on getting at. Thank you again.
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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