This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A115515 #10 Apr 10 2019 10:34:26
%S A115515 0,3,10,30,82,226,615,1673,4549,12366,33616,91379,248396,675213,
%T A115515 1835420,4989190,13562026,36865411,100210580,272400599,740461600,
%U A115515 2012783314,5471312309,14872568830,40427833595,109894245428
%N A115515 a(n) = largest m such that the harmonic number H(m)= Sum_{i=1..m} 1/i is < n.
%H A115515 H. P. Robinson, <a href="/A006530/a006530.pdf">Letter to N. J. A. Sloane, Oct 1981</a>
%p A115515 c:=0: H[0]:=0: for n from 1 to 10^4 do H[n]:=1/n+H[n-1]: if floor(H[n])-floor(H[n-1])=1 then c:=1+c: b[c]:=n-1: else c:=c: fi: od: seq(b[j],j=1..c); # _Emeric Deutsch_
%t A115515 a[n_] := Ceiling[k /. FindRoot[HarmonicNumber[k] == n, {k, Exp[n]}, WorkingPrecision -> 100]] - 1;
%t A115515 Array[a, 26] (* _Jean-François Alcover_, Apr 10 2019 *)
%Y A115515 Apart from the initial values, this is simply A002387(n)-1. Cf. A004080.
%K A115515 nonn
%O A115515 1,2
%A A115515 _Artur Jasinski_, Jan 23 2006