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 A327845 Number of permutations of {1,2,...,n} such that for every k >= 1, the k-th differences are distinct. 2
 1, 2, 4, 12, 40, 132, 428, 1668, 7628, 36924, 199000, 1161824, 7231332 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) <= A131529(n). LINKS Table of n, a(n) for n=1..13. EXAMPLE For n = 5 the a(5) = 40 solutions are one of following ten permutations, or a reversal, complement, or reversal and complement of one of these permutations: [1,3,4,2,5] [1,4,3,5,2] [1,4,5,3,2] [1,5,2,4,3] [1,5,3,2,4] [2,1,4,5,3] [2,1,5,3,4] [2,3,5,1,4] [2,4,1,5,3] [2,5,4,1,3] As a non-example, [1,5,4,2,3] does not satisfy the k-th differences property, because while its first differences ([4,-1,-2,1]) and its second differences ([-5,-1,3]) are distinct, its third differences ([4,4]) are not. CROSSREFS Cf. A130783, A131529, A327743. Sequence in context: A126946 A113179 A214761 * A056236 A300652 A028329 Adjacent sequences: A327842 A327843 A327844 * A327846 A327847 A327848 KEYWORD nonn,more AUTHOR Peter Kagey, Sep 27 2019 EXTENSIONS a(11) from Giovanni Resta, Sep 29 2019 a(12)-a(13) from Freddy Barrera, Oct 07 2019 STATUS approved

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Last modified November 30 01:30 EST 2023. Contains 367452 sequences. (Running on oeis4.)