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# Three-digit Primes

December 25, 1988

"All three-digit primes have zero as the middle digit" (Book Review, Dec. 11)? You should get a deluge of mail on this one. Start with 113, 127, 131. . . . Of 143 three-digit primes, 15 have a zero in the middle: about the expected number. If this mistake is in Bernard O'Keefe's book ("Trapdoor") rather than in Jack Miles' review, I would not believe any mathematics the author uses.

GEORGE W. ABBOTT JR.

HAWTHORNE

Editor's note: The sentence should have read: "All three-digit primes with a zero have zero as the middle digit," and Bernard O'Keefe does not make the same mistake. The relevant passage in "Trapdoor" reads:

" 'You've got it,' replied Kane. 'The two primes she transmitted to the Israelis had zeros in them. I'm convinced now that she assembled her large prime numbers from small ones. One- and two-digit primes have no zeros. In three-digit numbers the zeros would have to be in the middle. There are only fifteen of them, which she could memorize. How brilliant! She built up a fifty-digit series from only fifteen small numbers. This will cut hours out of the search. I'll get on the programmers right away' " (Page 279).