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Sam Loyd's Cyclopedia of Puzzles
A picture of frustration: Sam Loyd's 15 puzzle – David Richeson: Division by Zero
Sam Loyd - Linda Hall Library
This is THE DISAPPEARING BICYCLIST puzzle by 18th Century mathematician Sam Loyd. In position 'A' 13 boys are visible, but in position 'B' - only 12. One is invited to determine which