We haven't reached a complete consensus on whether or not
Ans is permitted as a valid input format for TI-BASIC.
We have this answer on "Default for Code Golf: Input/Output methods" with a slim majority support for its use, but I recently posted an answer to Approximation of e which used
Ans as input, receiving a large amount of dispute over the matter.
The previous meta post answer also cites another TI answer using
Ans that was questioned heavily. Though that should prohibit the use of
Ans, some have stated that
Ans has historically been used without issue.
Ans permitted as a valid form of input, or not?