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PROJECT EULER · #0989

Fibonacci Sum

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Write Fn for the n-th Fibonacci number, with F1=F2=1 and Fn+1=Fn+Fn1.

It is known that Fn is very well approximated by φn/5, where φ, the golden ratio, is the positive root of the equation x2=x+1.

Let G(n) be the number of distinct integers 0x<n such that x2x+1(modn).

You are given n=1103FnG(n)190950976mod(109+9).

Find n=11014FnG(n), giving your answer modulo 109+9.

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