# Not Double Factorial

Algebra Level 3

$\frac { 1 }{ 1 \times 3 } +\frac { 2 }{ 1 \times 3 \times 5 } +\frac { 3 }{ 1 \times 3 \times 5 \times 7 } + \frac { 4 }{ 1 \times 3 \times 5 \times 7 \times 9 } +\ldots$

Find the sum of the series above.

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