12 Days of Christmas
42nd
99 Bottles of Beer
20th
Arabic to Roman
56th
Christmas Trees
16th
Cubes
12th
Diamonds
14th
Divisors
27th
Emirp Numbers
23rd
Evil Numbers
29th
Fibonacci
28th
Fizz Buzz
19th
Fractions
14th
Leap Years
16th
Odious Numbers
28th
Pernicious Numbers
18th
Quine
1st817th
Sierpiński Triangle
15th
Spelling Numbers
62nd
Tongue-twisters
12th
λ
11th