Fermat claimed a proof he had no room to write down, and it took three centuries to find.

What it means

The claim is that no whole numbers solve the equation for a power above two, and Fermat wrote in a book margin that he had a marvelous proof the margin was too narrow to hold. Andrew Wiles announced one in 1993, withdrew it when a gap appeared, and completed the repair a year later. The finished argument runs to over a hundred pages of machinery invented long after Fermat died, so whatever he had, it was not this.

The claim comes from MacTutor History of Mathematics.

Nearby in the collection

The facts either side of this one.

• MacTutormedium, 73 letters
• Wolfram MathWorldhard, 70 letters
• MacTutorhard, 68 letters
• MacTutorhard, 69 letters

About as hard as this one

Scored closest to it by the model behind our guide to solving cryptograms.

• Wolfram MathWorldmedium, 81 letters
• Wolfram MathWorldmedium, 74 letters
• OEISmedium, 71 letters
• NISTmedium, 72 letters