# This doesn't look nice...

Algebra Level 5

Given that the value of

$\sum _ { i = 1 } ^ { \infty } \frac {1 \times 4 \times 7 \times \ldots \times ( 3i - 2 ) } { 6 \times 12 \times 18 \times \ldots \times 6i }$

can be expressed in the form $$\sqrt [ 15 ] { a } - \sqrt [ 15 ] { b }$$, where $$a$$ and $$b$$ are positive integers, find the smallest possible value of $$ab$$.

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