A211200 - OEIS

%I #26 Mar 18 2014 05:35:29

%S 1,11,113,7103,8778881,2302890927539,7289913993299309016859,

%T 330513634706872709970497049176749987771,

%U 52698433600606388974675914778280598904460888679269021907794061677149

%N Indices of records in A207709.

%C Least k such that (H(k) + exp(H(k))*log(H(k)))/sigma(k) >= n, where H(k) is the harmonic number sum_{i=1..k} 1/i.

%C a(10) has 119 digits and is too large to include.

%C Conjecture: the sequence contains only noncomposite numbers.

%e A207709(11) = 2 since A207709(113) = 3 is the next record value.

%t lst = {}; h = k = n = 0; Do[While[n <= max, k++; h = h + 1/k; n = (h + Exp@h*Log@h)/DivisorSigma[1, k]]; AppendTo[lst, k], {max, 2, 4}]; Prepend[lst, 1]

%Y Cf. A207709.

%K nonn

%O 1,2

%A _Arkadiusz Wesolowski_, Apr 04 2012