Every integer minus any permutation of its digits is divisible by nine.
A few example clues from my favorite type of crossword.
Can you solve a puzzle hidden within a cover letter?
We discuss the linear-time algorithm for computing the satisfiability of a 2-CNF formula.
We determine whether polyhedra can be efficiently checked for boundedness using a fundamental idea from linear algebra.
A brief sketch of the proof that chess is EXPTIME-Complete.
Every integer minus its reversal is divisible by nine.