Number Series Puzzles · Billy-B
Number Series #13
From Billy-B's legendary 1001 Puzzle Collection — preserved on Puzz.com since 1998.
Puzzle #13
15 11 9 5 3 1 ?
Reveal Answer
15 11 9 5 3 1 0 The series is of the prime numbers in reverse order, beginning with 17, but 2 was subtracted from each number.
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