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 A110566 a(n) = lcm{1,2,...,n}/denominator of harmonic number H(n). 20
 1, 1, 1, 1, 1, 3, 3, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 15, 45, 45, 45, 15, 3, 3, 1, 1, 1, 1, 1, 1, 11, 11, 11, 11, 11, 11, 11, 11, 11, 77, 77, 7, 7, 7, 7, 7, 1, 1, 1, 1, 1, 3, 3, 3, 3, 3, 3, 3, 3, 3, 9, 9, 9, 27, 27, 27, 9, 9, 9, 3, 3, 3, 3, 3, 33, 33, 33, 33, 11, 11, 11, 11, 11, 11, 11, 1, 1, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,6 COMMENTS a(n) is always odd. Unsorted union: 1, 3, 15, 45, 11, 77, 7, 9, 27, 33, 25, 5, 55, 275, 13, 39, 17, 49, 931, 19, 319, 75, ..., . See A112810. Also gcd(lcm{1,2,...,n}, H(n)*lcm{1,2,...,n}). - Franz Vrabec, Sep 21 2005 LINKS Alois P. Heinz, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A003418(n)/A002805(n) = A025529(n)/A001008(n). a(n) = gcd(A003418(n), A025529(n)). - Franz Vrabec, Sep 21 2005 EXAMPLE a(6) = 60/20 = 3 because lcm{1,2,3,4,5,6}=60 and H(6)=49/20. MAPLE H:= proc(n) H(n):= 1/n +`if`(n=1, 0, H(n-1)) end: L:= proc(n) L(n):= ilcm(n, `if`(n=1, 1, L(n-1))) end: a:= n-> L(n)/denom(H(n)): seq(a(n), n=1..100);  # Alois P. Heinz, Aug 30 2012 MATHEMATICA f[n_] := LCM @@ Range[n]/Denominator[HarmonicNumber[n]]; Table[ f[n], {n, 90}] (* Robert G. Wilson v *) PROG (PARI) a(n) = lcm(vector(n, k, k))/denominator(sum(k=1, n, 1/k)); \\ Michel Marcus, Mar 07 2018 CROSSREFS Cf. A001008, A002805, A003418, A025529, A098464, A112822. Sequence in context: A019801 A086634 A066601 * A126066 A177693 A131289 Adjacent sequences:  A110563 A110564 A110565 * A110567 A110568 A110569 KEYWORD nonn AUTHOR Franz Vrabec, Sep 12 2005 EXTENSIONS More terms from Robert G. Wilson v, Sep 15 2005 STATUS approved

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Last modified July 22 20:51 EDT 2019. Contains 325226 sequences. (Running on oeis4.)