Here's an attempt to proof the following claim that I saw in @CompSciFact's Tweet earlier today.
(in case you don't know already, I am on twitter, find me @SubhayanRM :) )
Claim:
Let F[n] be the nth Fibonacci number.
Then F[0] + F[1] + ... + F[n] = F[n+2] - 1.
Proof: (By induction)
We deine F[ i ] = F[ i - 1 ] + F[ i - 2 ]
and F[-1] = 1
F[-2] = 0
i.e. We start from 1. i.e F = 1,2,3,5,8, ...
however the proof is valid even if the you want to start from F=0,1,1,2 .. , just change the base case :), which is trivial and certainly holds true.
"I leave it up to the reader to verify" ;)
The inductive hypothesis and the proof of it will be the same.
Base Case:
for n=1
we have F[1] = 1 = 2-1 = F[2]-1
so the base case holds true
Inductive Hypothesis: For purposes of induction we assume that proposition
P(n) = F[0] + F[1] + ... + F[n ] = F[n+2] - 1
is true
so,
P(n+1)
= F[0] + F[1] + ... + F[k ] + F[k+1]
= F[k+2] - 1 + F[k + 1]
= F[k+1] + F[k+2] - 1
= F[k+3] - 1
= F[(k+1) + 2] - 1
So by laws of mathematical induction, P(n+1) is true whenever P(n) is true. \qed