12 Days of Christmas
9th
99 Bottles of Beer
12th
Arabic to Roman
7th
Christmas Trees
10th
Divisors
31st
Emirp Numbers
11th
Evil Numbers
19th
Fibonacci
50th
Fizz Buzz
75th
Happy Numbers
9th
Niven Numbers
41st
Odious Numbers
18th
Pascal’s Triangle
14th
Pernicious Numbers
19th
Prime Numbers
34th
Quine
1st
Roman to Arabic
9th
Seven Segment
9th
Sierpiński Triangle
8th
π
11th