Create letter / number sequence dynamically in Excel

For Numbers:

=SEQUENCE(COUNTA(C:C)-1)

For Letters:

=LOWER(SUBSTITUTE(ADDRESS(1,SEQUENCE(COUNTA(C:C)-1,,1),4),1,""))

For Letters (LAMBDA):

=LAMBDA(range, LOWER(SUBSTITUTE(ADDRESS(1, SEQUENCE(range-1,,1),4), 1, "")))

YouTube:
https://youtu.be/_2NdB7yT-n0

GitHub:
https://github.com/havishmad/excel_dynamic_letter_number_sequence