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 A344403 #15 Jun 12 2025 17:10:04
%S A344403 1,2,3,6,5,8,7,12,12,14,11,21,13,20,18,28,17,32,19,34,27,32,23,46,30,
%T A344403 38,36,46,29,58,31,56,42,50,40,80,37,56,51,73,41,80,43,74,65,68,47,
%U A344403 105,56,84,66,90,53,104,65,103,75,86,59,136,61,92,91,120,75,125,67,118,90
%N A344403 a(n) = Sum_{d|n} d * floor(n/d^2).
%C A344403 If p is prime, a(p) = Sum_{d|p} d * floor(p/d^2) = 1*p + p*0 = p.
%F A344403 G.f.: Sum_{k>=1} k*x^(k^2)/((1 - x^k)*(1 - x^(k^2))). - _Miles Wilson_, Jun 11 2025
%e A344403 a(6) = 8; Sum_{d|6} d * floor(6/d^2) = 1*6 + 2*1 + 3*0 + 6*0 = 8.
%t A344403 Table[Sum[(1 - Ceiling[n/k] + Floor[n/k]) k*Floor[n/k^2], {k, n}], {n, 100}]
%o A344403 (PARI) a(n) = sumdiv(n, d, d*(n\d^2)); \\ _Michel Marcus_, May 17 2021
%Y A344403 Cf. A344128, A344404, A344405.
%K A344403 nonn
%O A344403 1,2
%A A344403 _Wesley Ivan Hurt_, May 16 2021