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 A307728 #63 Jun 16 2020 14:51:31
%S A307728 0,0,3,0,5,6,7,8,18,20,22,24,39,28,60,48,85,72,95,100,105,132,138,144,
%T A307728 175,182,243,224,290,270,310,320,363,408,420,432,518,494,624,560,697,
%U A307728 672,731,792,810,920,940,960,1078,1100,1224,1196,1325,1404,1430
%N A307728 Sum of the perimeters of all acute integer triangles with perimeter n.
%H A307728 Wikipedia, <a href="https://en.wikipedia.org/wiki/Integer_triangle">Integer Triangle</a>
%F A307728 a(n) = n * A070093(n).
%F A307728 a(n) = n * Sum_{k=1..floor(n/3)} Sum_{i=k..floor((n-k)/2)} (1-sign(floor((n-i-k)^2/(i^2+k^2)))) * sign(floor((i+k)/(n-i-k+1))).
%t A307728 Table[n*Sum[Sum[(1 - Sign[Floor[(n - i - k)^2/(i^2 + k^2)]]) Sign[Floor[(i + k)/(n - i - k + 1)]], {i, k, Floor[(n - k)/2]}], {k, Floor[n/3]}], {n, 100}]
%Y A307728 Cf. A070093.
%K A307728 nonn
%O A307728 1,3
%A A307728 _Wesley Ivan Hurt_, May 15 2019