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 A157279 Product 1*2*...*r mod n, where r = integer part of sqrt(n). 0
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,4 LINKS FORMULA a(n) = (floor(sqrt(n)))! mod n. EXAMPLE a(17) = (floor(sqrt(17)))! mod 17 = (floor(4.12...))! mod 17 = 4! mod 17 = 24 mod 17 = 7. MATHEMATICA Table[Mod[Floor[Sqrt[n]]!, n], {n, 90}] (* Harvey P. Dale, Feb 15 2022 *) PROG (MAGMA) [ Factorial(Floor(Sqrt(n))) mod n: n in [1..84] ]; CROSSREFS Cf. A000142 (factorial numbers), A000196 (integer part of square root of n). Sequence in context: A343122 A338869 A104588 * A214080 A278241 A010671 Adjacent sequences:  A157276 A157277 A157278 * A157280 A157281 A157282 KEYWORD nonn AUTHOR Thomas Kerscher (Thomas.Kerscher(AT)web.de), Feb 26 2009 EXTENSIONS Edited and a(1) corrected by Klaus Brockhaus, May 27 2009 STATUS approved

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Last modified July 4 06:51 EDT 2022. Contains 355065 sequences. (Running on oeis4.)