Numerical Crossword

For many years, a rather difficult version of this puzzle could be found only in 'Tough Puzzles', the subscription-only magazine for puzzle experts that made MENSA's best efforts seem like child's play. It was one of the most challenging and popular of puzzles, created by Barbara Holmes. Other compilers have attempted to create Numerical Crosswords, but none has managed to match Barbara's puzzles.

At first sight, many of the clues seem deadpan (eg, 'Palindromic number'; or 'All digits are the same'; or 'Square number'). One or two appear downright baffling (eg, 'Product of the last 2 digits equals 4 times the total of the first 3 digits'). Most of the others are cross-referenced in an elaborate way (eg, 'Difference between the first and last pairs of digits of 39 down'; or 'Only 2 different digits are used; the total equals 2 digits from 32 down'). What makes Barbara's puzzles remarkable is the way in which, in spite of the level of obfuscation, they unfold for the determined solver.

A slightly sawn-off version of this beautiful puzzle has been introduced recently in 'Puzzler Collection', and it has been welcomed with enthusiasm by readers.