The Euler function and other problems in number theory


Euler function

The theory can be read here.

Modulo Fibonacci numbers

To efficiently find the Fibonacci number, we use matrix multiplication, more details here.
 
Knowing that 
\(F_{n+m} = F_m F_{n+1} + F_{m-1} F_n\), write the recurrence relation for matrix product:
• if \(m = n\) then \(F_{2n} = F_n F_{n+1} + F_ {n-1} F_n\);
• if \(m = n + 1\) then \(F_{2n+1} = F_{n+1 } F_{n+1} + F_n F_n\).