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 A124443 a(1)=1, a(n) = LCM of the integers, from 1 to n/2, which are coprime to n. 2
 1, 1, 1, 1, 2, 1, 6, 3, 4, 3, 60, 5, 60, 15, 28, 105, 840, 35, 2520, 63, 40, 315, 27720, 385, 5544, 3465, 40040, 6435, 360360, 1001, 360360, 45045, 7280, 45045, 350064, 85085, 12252240, 765765, 1989680, 2909907, 232792560, 230945, 232792560, 1322685 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 LINKS EXAMPLE The integers which are >= 1 and are <= 9/2 and which are coprime to 9 are 1, 2 and 4. So a(9) = lcm(1,2,4) = 4. MATHEMATICA f[n_] := If[n == 1, 1, LCM @@ Select[Range[Floor[n/2]], GCD[ #, n] == 1 &]]; Table[f[n], {n, 45}] (* Ray Chandler, Nov 12 2006 *) PROG (PARI) a(n) = lcm(select(x->(gcd(x, n)==1), vector(n\2, k, k))); \\ Michel Marcus, Mar 18 2018 CROSSREFS Cf. A124444. Sequence in context: A131449 A289869 A334595 * A077172 A160047 A249990 Adjacent sequences:  A124440 A124441 A124442 * A124444 A124445 A124446 KEYWORD nonn AUTHOR Leroy Quet, Nov 01 2006 EXTENSIONS Extended by Ray Chandler, Nov 12 2006 STATUS approved

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Last modified June 22 16:35 EDT 2021. Contains 345388 sequences. (Running on oeis4.)