- algorithm approximation bar binary binomial coefficients book cards carnival Carnival of Mathematics chocolate circle coins complex conjecture convolution counting decadic decimal diagrams Dirichlet factorization fibonacci fractal game games graph groups Haskell hyperbinary idempotent integers interactive irrational Ivan Niven Lagrange lehmer lucas MaBloWriMo making Mersenne moebius mu multiplication nim notation number numbers objects omega order pi powers prime primes primitive programming proof puzzle review roots sequence square strategy sum symmetry test tree triangular two-player unit unity video visualization X zero-sum
### Blogroll

### Fun

### Reference

### Categories

- algebra (46)
- arithmetic (63)
- books (29)
- calculus (7)
- challenges (53)
- combinatorics (12)
- complex numbers (6)
- computation (46)
- convergence (9)
- counting (32)
- famous numbers (48)
- fibonacci (18)
- fractals (13)
- games (34)
- geometry (56)
- golden ratio (8)
- group theory (26)
- humor (6)
- induction (7)
- infinity (19)
- iteration (24)
- links (74)
- logic (6)
- meta (41)
- modular arithmetic (24)
- number theory (76)
- open problems (11)
- paradox (1)
- pascal's triangle (8)
- pattern (91)
- people (21)
- pictures (69)
- posts without words (24)
- primes (35)
- probability (6)
- programming (17)
- proof (69)
- puzzles (15)
- recursion (16)
- review (20)
- sequences (28)
- solutions (28)
- teaching (14)
- trig (3)
- Uncategorized (6)
- video (19)

### Archives

- July 2017 (3)
- June 2017 (4)
- May 2017 (9)
- April 2017 (7)
- March 2017 (5)
- February 2017 (4)
- January 2017 (3)
- December 2016 (4)
- November 2016 (6)
- October 2016 (6)
- September 2016 (2)
- August 2016 (5)
- July 2016 (2)
- June 2016 (4)
- May 2016 (4)
- April 2016 (2)
- March 2016 (3)
- February 2016 (9)
- January 2016 (8)
- December 2015 (5)
- November 2015 (29)
- August 2015 (3)
- June 2015 (2)
- April 2015 (1)
- May 2014 (1)
- December 2013 (1)
- October 2013 (1)
- July 2013 (1)
- June 2013 (1)
- May 2013 (1)
- April 2013 (3)
- March 2013 (3)
- February 2013 (2)
- January 2013 (5)
- December 2012 (3)
- November 2012 (4)
- October 2012 (5)
- September 2012 (1)
- August 2012 (4)
- July 2012 (1)
- June 2012 (6)
- May 2012 (2)
- April 2012 (3)
- March 2012 (1)
- February 2012 (4)
- January 2012 (5)
- December 2011 (1)
- November 2011 (7)
- October 2011 (4)
- September 2011 (6)
- July 2011 (2)
- June 2011 (4)
- May 2011 (5)
- April 2011 (2)
- March 2011 (4)
- February 2011 (1)
- January 2011 (1)
- December 2010 (1)
- November 2010 (4)
- October 2010 (2)
- September 2010 (1)
- August 2010 (1)
- July 2010 (1)
- June 2010 (2)
- May 2010 (3)
- April 2010 (1)
- February 2010 (6)
- January 2010 (3)
- December 2009 (8)
- November 2009 (7)
- October 2009 (3)
- September 2009 (3)
- August 2009 (1)
- June 2009 (4)
- May 2009 (5)
- April 2009 (4)
- March 2009 (2)
- February 2009 (1)
- January 2009 (7)
- December 2008 (1)
- October 2008 (2)
- September 2008 (7)
- August 2008 (1)
- July 2008 (1)
- June 2008 (1)
- April 2008 (5)
- February 2008 (4)
- January 2008 (4)
- December 2007 (3)
- November 2007 (12)
- October 2007 (2)
- September 2007 (4)
- August 2007 (3)
- July 2007 (1)
- June 2007 (3)
- May 2007 (1)
- April 2007 (4)
- March 2007 (3)
- February 2007 (7)
- January 2007 (1)
- December 2006 (2)
- October 2006 (2)
- September 2006 (6)
- July 2006 (4)
- June 2006 (2)
- May 2006 (6)
- April 2006 (3)
- March 2006 (6)

### Meta

# Monthly Archives: June 2011

## Happy Tau Day!

Happy day! , of course, is the fundamental circle constant which represents the ratio of any circle’s circumference to its radius. (In the past people have also used the symbol “” to represent half of ; perhaps you’ve heard of … Continue reading

## The wonderful world of Mike Reilly

The other day I received an email from Mike Reilly, who introduced himself as a professional game and puzzle inventor, and suggested that I might be interested in taking a look at a few of his web sites. I wasn’t … Continue reading

## The Collatz conjecture is safe (for now)

A few days ago John Cook reported a draft paper claiming to solve the Collatz conjecture. Of course, since the Collatz conjecture is so simple to state, it constantly attracts tons of would-be solvers, and most of the purported “proofs” … Continue reading

Posted in open problems, proof
43 Comments