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A228621
Number of s in {1,...,n}^n having shortest run with the same value of length 2.
2
2, 0, 12, 40, 210, 840, 5208, 23760, 148410, 786720, 5137440, 30051528, 207058488, 1318599240, 9540828480, 65319695136, 495194683680, 3608366801040, 28572937581140, 219952629498840, 1813839842408748, 14663194937503288, 125593649761912704, 1061139859894326000
OFFSET
2,1
LINKS
EXAMPLE
a(2) = 2: [1,1], [2,2].
a(4) = 12: [1,1,2,2], [1,1,3,3], [1,1,4,4], [2,2,1,1], [2,2,3,3], [2,2,4,4], [3,3,1,1], [3,3,2,2], [3,3,4,4], [4,4,1,1], [4,4,2,2], [4,4,3,3].
CROSSREFS
Column k=2 of A228617.
Sequence in context: A112261 A134831 A074001 * A180189 A182437 A326860
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 28 2013
STATUS
approved