Print numbers from 1 to 100 with fizzbuzz rules

Display the alphabet with each letter repeated twice, alternating case per pair

Display the alphabet in reverse with case alternating in pairs of two

int days_in_month(int year, int month)

int digit_count(int n)

Display the multiplication table of the given positive integer

Draw one bar of '#' per integer argument, one bar per line

Draw a centered pyramid of '#' whose height comes from the argument

Repeat each letter by its 0-based alphabetical position

Print a single argument from its last character back to its first