12 Days of Christmas
10th
99 Bottles of Beer
9th
Abundant Numbers
33rd
Christmas Trees
6th
CSS Colors
5th
Diamonds
6th
Divisors
13th
Emirp Numbers
Fibonacci
52nd
Fizz Buzz
28th545th1,515th
Happy Numbers
37th
Intersection
5th
Leap Years
16th
Morse Decoder
3rd
Morse Encoder
4th
Niven Numbers
40th
Prime Numbers
39th
Seven Segment
5th
Sierpiński Triangle
12th
Tongue-twisters
18th
United States
7th