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A333082
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Number of permutations sigma of [n] such that all values sigma(k)/k for 1 <= k <= n are pairwise distinct.
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2
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1, 1, 1, 5, 13, 79, 345, 2785, 19595, 171141, 1555181, 18998391, 184988197, 2675065491, 35582840563, 490186693669
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OFFSET
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0,4
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LINKS
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MATHEMATICA
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Table[ Count[ Length[ Union[ #/ Range[n]]] & /@ Permutations[ Range@n], n], {n, 0, 9}] (* Giovanni Resta, Mar 09 2020 *)
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PROG
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(Ruby)
def A(n)
(1..n).to_a.permutation.select{|i| (1..n).map{|j| i[j - 1] / j.to_r}.uniq.size == n}.size
end
(0..n).map{|i| A(i)}
end
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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