We get the sequence of Fibonacci numbers by slightly changing the binary number system – let’s do the conversion. Example:
How we will transform: we will replace zeros with ones, ones with twos, then we sum them up.
Let’s write in two columns the numbers before the conversion, and after:
; ; ; ; ; ; ; ; ; ; ;
The numbers on the right are repeated, let’s count their repetitions:
; ; ; ; ; ; ; ;
We get a sequence of Fibonacci numbers.
To derive a formula for Fibonacci numbers, you need to count the number of repetitions of the number. I note that each repeated number (converted from a binary number) occurs in the natural series of numbers in the interval ; ;
Let’s take the repeating number as an example. In how many ways can we write the number as a sum of twos and ones?
Subtract one deuce from each of the options:
For each case, we calculate the number of combinations from (the number of numbers) by (the number of twos), and sum them up. We get:
Wikipedia only mentions diagonal summation in Pascal’s triangle.