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A090588
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Number of labeled idempotent groupoids.
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6
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1, 1, 4, 729, 16777216, 95367431640625, 221073919720733357899776, 311973482284542371301330321821976049, 374144419156711147060143317175368453031918731001856, 507528786056415600719754159741696356908742250191663887263627442114881
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n) = n^(n^2 - n).
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MAPLE
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a:=n->mul(mul(sum(1, j=1..n), k=1..n), m=1..n-1): seq(a(n), n=0..8); # Zerinvary Lajos, Dec 31 2008
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MATHEMATICA
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Join[{1}, Table[n^(n^2-n), {n, 10}]] (* Harvey P. Dale, Sep 16 2013 *)
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PROG
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(Ruby)
def a(n)
ids =* (0..n-1)
return (ids.product(ids)).reduce(1){ |accum, x| (x[0] == x[1]) ? accum : accum*ids.length}
end
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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