login
Numbers k such that lcm(1,2,3,...,k)/11 equals the denominator of the k-th harmonic number H(k).
12

%I #19 Jan 31 2021 02:38:09

%S 33,34,35,36,37,38,39,40,41,81,82,83,84,85,86,87,363,364,365,366,367,

%T 368,369,370,371,372,373,374,375,376,406,407,408,409,410,411,412,413,

%U 414,415,416,417,418,419,420,421,422,423,424,425,426,427,428,429,430

%N Numbers k such that lcm(1,2,3,...,k)/11 equals the denominator of the k-th harmonic number H(k).

%C When 11 occurs in A110566.

%H Amiram Eldar, <a href="/A112817/b112817.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Jinyuan Wang)

%t f[n_] := LCM @@ Range[n]/Denominator[ HarmonicNumber[n]]; Select[ Range[430], f[ # ] == 11 &]

%t Select[Range[450],1/11*LCM@@Range[#]==Denominator[HarmonicNumber[#]]&] (* _Harvey P. Dale_, Jan 06 2019 *)

%Y Cf. A002805, A003418, A110566.

%Y Cf. A098464, A112813, A112814, A112815, A112816, A112818, A112819, A112820, A112821, A112822.

%K nonn

%O 1,1

%A _Robert G. Wilson v_, Sep 17 2005

%E Name (definition) corrected by _Harvey P. Dale_, Jan 06 2019