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A000303 Number of permutations of [n] in which the longest run has length 2.
(Formerly M3522 N1430)
+0
2
1, 4, 16, 69, 348, 2016, 13357, 99376, 822040, 7477161, 74207208, 797771520, 9236662345, 114579019468, 1516103040832, 21314681315997 (list; graph; listen)
OFFSET

2,2

REFERENCES

F. N. David, M. G. Kendall and D. E. Barton, Symmetric Function and Allied Tables, Cambridge, 1966, p. 261, Table 7.4.1.

EXAMPLE

a(3)=4 because we have (13)2, 2(13), (23)1, 3(12), where the parentheses surround runs of length 2.

CROSSREFS

Column 2 of A008304.

Sequence in context: A128730 A006319 A059606 this_sequence A133789 A091354 A124533

Adjacent sequences: A000300 A000301 A000302 this_sequence A000304 A000305 A000306

KEYWORD

nonn

AUTHOR

njas

EXTENSIONS

Better description from Emeric Deutsch (deutsch(AT)duke.poly.edu), May 08 2004

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Last modified July 25 07:41 EDT 2008. Contains 142293 sequences.


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