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 A339918 #12 Dec 23 2020 06:43:47
%S A339918 0,3,9,16,25,33,43,53,64,73,86,96,110,118,133,145,158,169,182,196,211,
%T A339918 221,237,247,266,276,291,306,321,331,350,362,379,391,407,423,438,450,
%U A339918 467,481,502,511,530,542,561,575,590,606,626,638,655,669,690,698,721
%N A339918 a(n) = Sum_{k=1..n} floor(3*n/k).
%C A339918 In general, for m>=1, Sum_{k=1..n} floor(m*n/k) ~ m*n * (log(m*n) + 2*gamma - H(m)), where H(m) = A001008(m)/A002805(m) is the m-th harmonic number and gamma is the Euler-Mascheroni constant A001620.
%H A339918 Vaclav Kotesovec, <a href="/A339918/b339918.txt">Table of n, a(n) for n = 0..10000</a>
%F A339918 a(n) ~ 3*n * (log(3*n) + 2*gamma - 11/6), where gamma is the Euler-Mascheroni constant A001620.
%t A339918 Table[Sum[Floor[3*n/k], {k, 1, n}], {n, 0, 100}]
%o A339918 (PARI) a(n) = sum(k=1, n, floor(3*n/k)); \\ _Michel Marcus_, Dec 23 2020
%Y A339918 Cf. A006218, A339217, A339919.
%K A339918 nonn
%O A339918 0,2
%A A339918 _Vaclav Kotesovec_, Dec 23 2020