Frontier Airlines Airbus A321neo accommodates 240 seats in an all Economy Class cabin.
Please note, the seat plan illustrated here while developed from Frontier's published diagram, has not yet been fully scrutinised by aeroLOPA so some discrepancies may be present albeit relatively minor. The seat count and raking on Frontier's diagram does coincide with the optimised high density layout published by Airbus

Diagram updated 12 Jun 2022
This aircraft type is fitted with 240 Recaro SL3710 lightweight slimline seats
Seat width: 17.7"
Row pitch:
Rows 2 to 3 (designated "Stretch" seats): 32"
Rows 4 to 17: 28.2"
Rows 18 and 19 ("Stretch"): 35"
Rows 20 to 28: 28.5"
Rows 30 to 41 ABC: 27.8"
Rows 30 to 40 DEF: 28.5"
Seats in exit row 29 offer greater legroom
Power: There are no seat power or USB sockets provided