%I #15 Jan 31 2021 02:38:24

%S 105,106,107,108,109,2625,2626,2627,2628,2629,2630,2631,2632,2633,

%T 2634,2635,2636,2637,2638,2639,2640,2641,2642,2643,2644,2645,2646,

%U 2647,2648,2649,2650,2651,2652,2653,2654,2655,2656,2657,2658,2659,2660,2661,2662

%N Numbers k such that lcm(1,2,3,...,k)/5 equals the denominator of the k-th harmonic number H(k).

%C When 5 occurs in A110566.

%H Amiram Eldar, <a href="/A112814/b112814.txt">Table of n, a(n) for n = 1..10000</a>

%t f[n_] := LCM @@ Range[n]/Denominator[ HarmonicNumber[n]]; Select[ Range[2662], f[ # ] == 5 &]

%o (PARI) isok(n) = lcm(vector(n, i, i)) == 5*denominator(sum(i=1, n, 1/i)); \\ _Michel Marcus_, Mar 07 2018

%Y Cf. A002805, A003418, A110566.

%Y Cf. A098464, A112813, A112815, A112816, A112817, A112818, A112819, A112820, A112821, A112822.

%K nonn

%O 1,1

%A _Robert G. Wilson v_, Sep 17 2005