What's up in

combinatorics

Mathematics

Theorists Draw Closer to Perfect Coloring

October 20, 2015

A theorem for coloring a large class of “perfect” mathematical networks could ease the way for a long-sought general coloring proof.

Q&A

The Connoisseur of Number Sequences

August 6, 2015

For more than 50 years, the mathematician Neil Sloane has curated the authoritative collection of interesting and important integer sequences.

Multimedia

The Nine Schoolgirls Challenge

June 9, 2015

Solve this variation of Thomas Kirkman’s famous 1850 puzzle by arranging girls in walking groups. And think fast — the clock is ticking.

Mathematics

A Design Dilemma Solved, Minus Designs

June 9, 2015

A 150-year-old conundrum about how to group people has been solved, but many puzzles remain.

Mathematics

For Persi Diaconis’ Next Magic Trick …

April 14, 2015

A mathematician who has analyzed card shuffling for decades is tackling one final nemesis: “smooshing.”