Symbols for "odd" and "even" Let $A$ be a sequence of letters $\langle a,b,c,d,e,f \rangle$. I want to create two subsequences, one with the values with odd index and other with the values with even index: $A_\mathrm{odd} = \langle a,c,e \rangle$ and $A_\mathrm{even} = \langle b,d,f \rangle$.
My question is: is there any usual symbol that could substitute the words "odd" and "even" in the name of the subsequence?
Thanks!

How about $A_\mathcal O$ and $A_\mathcal E$?
To produce these: A_\mathcal O and A_\mathcal E
