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 A338544 #16 Aug 19 2022 05:25:43
%S A338544 0,0,0,4,5,13,15,27,30,46,50,70,75,99,105,133,140,172,180,216,225,265,
%T A338544 275,319,330,378,390,442,455,511,525,585,600,664,680,748,765,837,855,
%U A338544 931,950,1030,1050,1134,1155,1243,1265,1357,1380,1476,1500,1600,1625,1729,1755,1863
%N A338544 a(n) = (5*floor((n-1)/2)^2 + (4+(-1)^n)*floor((n-1)/2)) / 2.
%C A338544 Sum of the largest side lengths of all integer-sided triangles with perimeter 3n whose side lengths are in arithmetic progression (for example, when n=5 there are two triangles with perimeter 3*5 = 15 whose side lengths are in arithmetic progression: [3,5,7] and [4,5,6]; thus a(5) = 7+6 = 13).
%H A338544 Wikipedia, <a href="https://en.wikipedia.org/wiki/Integer_triangle">Integer triangle</a>
%H A338544 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,-2,-1,1).
%F A338544 A147875 UNION A028895.
%F A338544 From _Stefano Spezia_, Nov 01 2020: (Start)
%F A338544 G.f.: x^3*(4 + x)/((1 - x)^3*(1 + x)^2).
%F A338544 a(n) = a(n-1) + 2*a(n-2) - 2*a(n-3) - a(n-4) + a(n-5) for n > 4. (End)
%F A338544 16*a(n) = -14*n-1+10*n^2+(-1)^n-6*(-1)^n*n . - _R. J. Mathar_, Aug 19 2022
%t A338544 Table[(5 Floor[(n - 1)/2]^2 + Floor[(n - 1)/2] (4 + (-1)^n))/2, {n, 0, 100}]
%Y A338544 Cf. A028895, A050187, A147875, A211539.
%K A338544 nonn,easy
%O A338544 0,4
%A A338544 _Wesley Ivan Hurt_, Nov 01 2020