# Almost Consecutive

Calculus Level 5

$1 + \frac {4}{6} + \frac {4 \cdot 5}{6\cdot 9}+ \frac {4 \cdot 5\cdot 6}{6\cdot 9\cdot 12} + \frac {4 \cdot 5\cdot 6 \cdot 7}{6\cdot 9\cdot 12 \cdot 15} + \ldots$

If the value of the series above is in the form of $$\frac a b$$ where $$a,b$$ are coprime positive integers, what is the value of $$a + b$$?

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