Solution 12148: Meaning of the @n Notation in an Answer on the TI-89 Family, TI-92 Family, and Voyage™ 200 Graphing Calculators.
What does the @ symbol mean in a answer on the TI-89 family, TI-92 family, and Voyage 200 graphing calculators?
The @ sign when displayed in an answer represents a constant.
For example, @n47*p means constant number 47 times p.
Each time an answer containing a constant is calculated the calculator assign a number to the constant. That number will increase by 1 for each subsequent answer until the history area of the Home screen is cleared. When an arbitrary integer occurs multiple times in the same session, each occurrence is numbered consecutively. After it reaches 255, arbitrary integer consecutive numbering restarts an @n0.
Please see the TI-89 family, TI-92 family and Voyage 200 guidebooks for additional information.