Ack! How did I miss this question for a few days?! I apologize.
Thank you for sharing your question, Laurie.
Your transcription is correct. It matches the print you shared exactly (i.e., A equals P open parenthesis one plus the fraction "r over n" close parenthesis superscript "nt").
You are very right that no grade 1 indicators are necessary for this expression.
The plus sign terminates the numeric mode initiated by the 1's numeric indicator. The grade 1 mode initiated by that same numeric indicator is in effect until the space after the closing braille grouping indicator. (third paragraph of GTM §1.2.2)