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 A339804 #24 Oct 27 2023 17:37:12
%S A339804 0,1,4,13,22,50,68,116,162,236,278,437,498,634,794,1018,1118,1450,
%T A339804 1574,1975,2276,2598,2774,3519,3834,4273,4746,5490,5772,6887,7214,
%U A339804 8163,8856,9586,10330,12072,12540,13443,14382,16244,16806,18861,19480,21192,22954,24267
%N A339804 a(n) = Sum_{k=1..floor(n/2)} k * (n-k) * floor((n-k)/k).
%C A339804 Total volume of all rectangular prisms with dimensions (x, y, z) where x and y are positive integers such that x + y = n, x <= y, and z = floor(y/x). - _Wesley Ivan Hurt_, Dec 20 2020
%F A339804 a(n) ~ n^3*(Pi^2-2-4*zeta(3))/12. - _Rok Cestnik_, Dec 19 2020
%F A339804 a(n) = n*A153485(n) - A279847(n). - _Vaclav Kotesovec_, Dec 21 2020
%t A339804 Table[Sum[k (n - k)*Floor[(n - k)/k], {k, Floor[n/2]}], {n, 50}]
%o A339804 (PARI) a(n) = sum(k=1, n\2, k*(n-k)*((n-k)\k)); \\ _Michel Marcus_, Dec 19 2020
%o A339804 (Python)
%o A339804 from math import isqrt
%o A339804 def A339804(n): return (n*(1-n**2)+((s:=isqrt(n))**4<<1)+s**3*(3*(1-n))+s**2*(1-3*n) + sum((q:=n//k)*(-6*k**2+n*(3*((k<<1)+q+1))-q*((q<<1)+3)-1) for k in range(1,s+1)))//6 # _Chai Wah Wu_, Oct 27 2023
%Y A339804 Cf. A002541, A153485, A279847, A339370.
%K A339804 nonn,easy
%O A339804 1,3
%A A339804 _Wesley Ivan Hurt_, Dec 17 2020