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 A307987 #40 Jun 16 2020 14:53:08
%S A307987 0,0,0,0,0,0,0,0,2,2,2,2,2,2,2,2,5,5,8,7,9,7,8,8,13,12,13,12,14,12,13,
%T A307987 13,19,18,19,19,24,24,24,24,30,31,31,31,32,32,32,33,39,40,46,46,49,47,
%U A307987 55,54,63,60,64,63,67,62,66,66,75,72,76,77,79,75,79
%N A307987 Number of integer-sided triangles with perimeter n and at least one nonsquarefree side.
%H A307987 Wikipedia, <a href="https://en.wikipedia.org/wiki/Integer_triangle">Integer Triangle</a>
%F A307987 a(n) = Sum_{k=1..floor(n/3)} Sum_{i=k..floor((n-k)/2)} sign(floor((i+k)/(n-i-k+1))) * (1 - mu(i)^2 * mu(k)^2 * mu(n-i-k)^2), where mu is the Möbius function (A008683).
%F A307987 a(n) = A005044(n) - A308061(n).
%t A307987 Table[Sum[Sum[(1 - MoebiusMu[i]^2*MoebiusMu[k]^2*MoebiusMu[n - i - k]^2)*Sign[Floor[(i + k)/(n - i - k + 1)]], {i, k, Floor[(n - k)/2]}], {k, Floor[n/3]}], {n, 100}]
%Y A307987 Cf. A005044, A008683, A308061.
%K A307987 nonn
%O A307987 1,9
%A A307987 _Wesley Ivan Hurt_, May 18 2019