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Next in Line (Posted on 2003-05-12) Difficulty: 3 of 5
What's the number that follows in this sequence, and what is the sequence's significance?

0,1,2,9,44,265,...

See The Solution Submitted by Charlie    
Rating: 2.3333 (6 votes)

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Solution Solution | Comment 8 of 9 |

The next number in the sequence is the recontres number
D7,0 and seventh subfactorial (!7), or in other words, the number of derangements of a set of seven elements, i.e., 1854.

The sequence can be found in "The On-line Encyclopedia of Integer Sequences" (Sloan's A000166).

!0 = 1, !1 = 0, !2 = 1, !3 = 2, !4 = 9, !5 = 44, !6 = 265,
!7 = 1854, !8 = 14833, !9 = 133496, ...


  Posted by Dej Mar on 2008-01-30 08:24:33
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