All thinkers

Elwyn Berlekamp: 2 puzzles worth knowing

2 puzzles from Elwyn Berlekamp, each explained in a minute and credited to the original work. Free on Savvy.

• Checkers jump toward a target row. Can they ever reach the fifth row up?

  Pegs sit on every square of an infinite checkerboard below a horizontal line. Each move takes one peg and jumps it over an adjacent peg in a straight line, removing the peg that wa…

  — John Conway, Elwyn Berlekamp, Richard Guy, Winning Ways for Your Mathematical Plays

• Name a number no one's named before — but never be the one who says 1

  Two players alternately call out a positive whole number that cannot be written as a sum of numbers already named (a number may be reused any number of times in that sum). For exam…

  — Elwyn Berlekamp, John Conway, Richard Guy, Winning Ways for Your Mathematical Plays

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