12 Days of Christmas
9th99 Bottles of Beer
5thAbundant Numbers
5thChristmas Trees
4thCubes
5thDiamonds
7thDivisors
1stEmirp Numbers
8thEvil Numbers
7thFibonacci
9thFizz Buzz
8thHappy Numbers
10thIntersection
5thKolakoski Constant
5thKolakoski Sequence
8thLeap Years
9thLeyland Numbers
4thLook and Say
6thMorse Decoder
4thMorse Encoder
5thNiven Numbers
1stOdious Numbers
7thPascal’s Triangle
6thPernicious Numbers
9thPrime Numbers
5thRecamán
6thSeven Segment
7thTongue-twisters
6thUnited States
5thVampire Numbers
5thλ
7thπ
7thτ
7thφ
9th√2
7th𝑒
7th