Ну и я уж :-)
import string
print([c*i for i,c in enumerate(string.ascii_lowercase,1)])
['a', 'bb', 'ccc', 'dddd', 'eeeee', 'ffffff', 'ggggggg', 'hhhhhhhh', 'iiiiiiiii', 'jjjjjjjjjj', 'kkkkkkkkkkk', 'llllllllllll', 'mmmmmmmmmmmmm', 'nnnnnnnnnnnnnn', 'ooooooooooooooo', 'pppppppppppppppp', 'qqqqqqqqqqqqqqqqq', 'rrrrrrrrrrrrrrrrrr', 'sssssssssssssssssss', 'tttttttttttttttttttt', 'uuuuuuuuuuuuuuuuuuuuu', 'vvvvvvvvvvvvvvvvvvvvvv', 'wwwwwwwwwwwwwwwwwwwwwww', 'xxxxxxxxxxxxxxxxxxxxxxxx', 'yyyyyyyyyyyyyyyyyyyyyyyyy', 'zzzzzzzzzzzzzzzzzzzzzzzzzz']