12 Days of Christmas
9th
99 Bottles of Beer
13th
Arabic to Roman
7th
Christmas Trees
11th
Divisors
33rd
Emirp Numbers
11th
Evil Numbers
20th
Fibonacci
54th
Fizz Buzz
79th
Happy Numbers
10th
Niven Numbers
45th
Odious Numbers
19th
Pascal’s Triangle
15th
Pernicious Numbers
19th
Prime Numbers
37th
Quine
1st
Roman to Arabic
10th
Seven Segment
10th
Sierpiński Triangle
9th
π
11th