# *Letters and Number Triangle Pattern* by @CodingComputing
from string import ascii_uppercase as alphas  # Alphabets
from string import digits  # String digits 0...9
natural_nums = digits[1:]  # String digits 1...9, because pattern starts from 1

height = 5  # height of the pattern
max_width = 2*height + (2*height-1)
# `height` number of alphabets, plus `height` number of digits,
# plus `2*height-1` number of spaces between characters

for row_idx in range(height):
    # Slice starting from row_idx, of (row_idx+1) items ahead
    row_slice = slice(row_idx, 2*row_idx+1)
    row_alphas = alphas[row_slice]  # slice out from alphas
    row_digits = natural_nums[row_slice]  # slice out from digits
    row_chars = row_alphas + row_digits  # characters to be printed in current row
    row_content = ' '.join(list(row_chars))  # insert spaces between chars
    print(f"{row_content:^{max_width}}")  # format to centre at max_width

# Output:
#         A 1
#       B C 2 3
#     C D E 3 4 5
#   D E F G 4 5 6 7
# E F G H I 5 6 7 8 9