Dianna Cowern: Bizarre spinning toys: PhiTOP

• PhiTOP
• Inertia
• Angular momentum
• Torque
• Right hand rule
• Gyroscopic Precession

Roger Bowley: 15 bumfit

1. Yan
2. Tan
3. Tethera
4. Pethera
5. Pimp
6. Sethera
7. Lethera
8. Hovera
9. Covera
10. Dik
11. Yan-a-dik
12. Tan-a-dik
13. Tethera-dik
14. Pethera-dik
15. Bumfit
16. Yan-a-bumfit
17. Tan-a-bumfit
18. Tethera-bumfit
19. Pethera-bumfit
20. Figgot

James Grime: 220 and 284: Amicable Numbers (友愛数)

Laurence Eaves: 69!: Factorial (階乗)

Laurence Eaves

OS X Calculator 92!

Roger Bowley: 6174: Kaprekar's Constant

Example:

7348

8743
3478
----------
5265

6552
2556
----------
3996

9963
3699
-----------
6264

6642
2466
-----------
4176

7641
1467
------------
6174


7641
1467
-------
6174

James Grime: 8128 and Perfect Numbers (完全数)

James Grime

Ria Symonds: 16: 16 and Square Number (平方数)

Ria Symonds

• Perfect square

Zvezdelina Stankova: Pebbling a Chessboard

Zvezdelina Stankova

James Grime: 11.11.11: 11 and Check digit in ISBN (ISBNのチェックディジット)

James Grime

Wrecker Ball Sequences

Bernardo Recamán Santos

What's the Next Number?

• Neil Sloane
• Catalan number (カタラン数)
• Recamán's Sequence (A005132)

The OEIS Movie

Tony Padilla: Six Sequences

Tony Padilla

Steve Mould: Measuring Coastline

Steve Mould

• Benoit Mandelbrot