A211200 Indices of records in A207709.

1, 11, 113, 7103, 8778881, 2302890927539, 7289913993299309016859, 330513634706872709970497049176749987771, 52698433600606388974675914778280598904460888679269021907794061677149

Offset

1,2

Comments

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.

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

Conjecture: the sequence contains only noncomposite numbers.

Links

Table of n, a(n) for n=1..9.

Example

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

Mathematica

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]

Crossrefs

Cf. A207709.

Sequence in context: A104096 A239821 A087391 * A048553 A110799 A088089

Adjacent sequences: A211197 A211198 A211199 * A211201 A211202 A211203

Keyword

nonn

Author

Arkadiusz Wesolowski, Apr 04 2012

Status

approved