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Old November 16th, 2008, 10:02 AM
clic-clac clic-clac is offline
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Well what we want to prove is that for every n \in \mathbb{N}, 3|H(n).
We know it's true for H(0) and H(1). Now, let k\geq 2 be an integer, and assume that H(k-2) and H(k-1) are divisible by 3.
We want to prove that 3 also divides H(k).

H(k)=2H(k-1) + H(k-2) - 6

So the question is: Is a sum of integers divisible by 3 divisible by 3?

If yes, the your proof is complete!
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