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A157279
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Product 1*2*...*r mod n, where r = integer part of sqrt(n).
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0
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0, 1, 1, 2, 2, 2, 2, 2, 6, 6, 6, 6, 6, 6, 6, 8, 7, 6, 5, 4, 3, 2, 1, 0, 20, 16, 12, 8, 4, 0, 27, 24, 21, 18, 15, 0, 17, 36, 18, 0, 23, 6, 32, 16, 0, 30, 15, 0, 42, 40, 42, 48, 5, 18, 35, 0, 24, 52, 25, 0, 38, 18, 0, 0, 20, 60, 53, 64, 24, 0, 63, 0, 24, 64, 45, 40, 49, 72, 30, 0, 0, 30, 4, 0
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OFFSET
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1,4
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LINKS
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FORMULA
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a(n) = (floor(sqrt(n)))! mod n.
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EXAMPLE
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a(17) = (floor(sqrt(17)))! mod 17 = (floor(4.12...))! mod 17 = 4! mod 17 = 24 mod 17 = 7.
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MATHEMATICA
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Table[Mod[Floor[Sqrt[n]]!, n], {n, 90}] (* Harvey P. Dale, Feb 15 2022 *)
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PROG
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(Magma) [ Factorial(Floor(Sqrt(n))) mod n: n in [1..84] ];
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CROSSREFS
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Cf. A000142 (factorial numbers), A000196 (integer part of square root of n).
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KEYWORD
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nonn
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AUTHOR
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Thomas Kerscher (Thomas.Kerscher(AT)web.de), Feb 26 2009
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EXTENSIONS
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STATUS
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approved
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