# Almost Consecutive

**Calculus**Level 4

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

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 \( a + b\)?