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A128438
a(n) = floor((denominator of H(n))/n), where H(n) = Sum_{k=1..n} 1/k, the n-th harmonic number.
3
1, 1, 2, 3, 12, 3, 20, 35, 280, 252, 2520, 2310, 27720, 25740, 24024, 45045, 720720, 226893, 4084080, 775975, 246341, 235144, 5173168, 14872858, 356948592, 343219800, 2974571600, 2868336900, 80313433200, 77636318760, 2329089562800
OFFSET
1,3
COMMENTS
This is very similar to A027611, which is a different sequence. - N. J. A. Sloane, Nov 21 2008
Indices where a(n) differs from A027611 are terms of A074791. - Gary Detlefs, Sep 03 2011
LINKS
EXAMPLE
The sequence denominator(H(n))/n begins 1, 1, 2, 3, 12, 10/3, 20, 35, 280, 252, 2520, 2310, ..., so the present sequence begins 1, 1, 2, 3, 12, 3, 20, 35, 280, 252, 2520, 2310, ...
MAPLE
H:=n->sum(1/k, k=1..n): a:=n->floor(denom(H(n))/n): seq(a(n), n=1..34); # Emeric Deutsch, Mar 25 2007
MATHEMATICA
seq = {}; s = 0; Do[s += 1/n; AppendTo[seq, Floor[Denominator[s]/n]], {n, 1, 30}]; seq (* Amiram Eldar, Sep 18 2021 *)
Table[Floor[Denominator[HarmonicNumber[n]]/n], {n, 40}] (* Harvey P. Dale, Nov 24 2023 *)
PROG
(Python)
from sympy import harmonic
def A128438(n): return harmonic(n).q//n # Chai Wah Wu, Sep 27 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Mar 03 2007
EXTENSIONS
More terms from Emeric Deutsch, Mar 25 2007
STATUS
approved