Question: what is pattern in this series

 

please help me in finding the pattersn in the series:

 

-1 / 6 + 1 / 20 - 5 / 84 + 7 / 216 - 47 / 1320 + 37 / 1560 - 319 / 12600 + 533/ 28560 - 1879 / 95760 + 1627 / 105840 --...

 

thanks

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