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A permutation puzzle (Posted on 2006-09-20) Difficulty: 3 of 5
Determine the number of permutations (p1, p2,...p7) of 1,2, ...7; such that for all k 1≤k≤6, (p1, p2,... pk) is not a permutation of (1,2, ...k); i.e., p1≠1; (p1, p2) is not a permutation of (1,2), etc.

What would be the answer if we specify 1≤k<6 instead?

No Solution Yet Submitted by K Sengupta    
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re: solution? - Nope Comment 4 of 4 |
(In reply to solution? by bumble)

Nope; the permutation (1,2,3,4,5,7,6) doesn't have 7 at the last position, but doesn't fulfill the other conditions.
  Posted by Old Original Oskar! on 2006-09-21 13:10:13

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