Question: number pattern sequence

Greetings All

I'm having some trouble figuring out a sequence of numbers using common Difference
I've figured out the polynomial for the even numbers for the sequence but the odd numbers have a repeating pattern which I'm not sure how to create a Polynomial for.  

I've included my work here
http://demos.onewithall.net/number_patterns.jpg on the even numbers which I’ve verified and they are correct.

I've included the odd numbers also I started doing the sequence of numbers using common Difference but as you can see I get a pattern of repeating numbers (-5,4).

How can I go about getting the polynomial for the odd numbers like I did for the even ones.


Tia sal2

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