The Chronicle Review

In Pursuit of the Impossible Equation

March 04, 2013 Premium content for subscribers. Subscribe Today

Imagine that a typical 9-by-9 Sudoku puzzle (in which the numbers 1 through 9 must appear exactly once in each row, column, and square) has been transformed into a 25-by-25 grid. The number of possibilities increases drastically, but while difficult...

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