# Too many Fractions and too much Infinity!

Algebra Level 4

$$\frac{3(\sum\limits_{n=4}^\infty \frac{(\lim_{x \to +\infty} \frac{1+2+3+...+x}{x ^ 2})}{2 ^ n})}{5}=\frac{a}{b}$$

$$gcd(a, b)=1$$

$$ab-1=x$$

What is the value of $$x$$?

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