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 A140144 #26 Jan 02 2024 09:00:15
%S A140144 1,2,5,6,11,12,19,20,29,30,41,42,55,56,71,72,89,90,109,110,131,132,
%T A140144 155,156,181,182,209,210,239,240,271,272,305,306,341,342,379,380,419,
%U A140144 420,461,462,505,506,551,552,599,600,649,650,701,702,755,756,811,812,869
%N A140144 a(1)=1, a(n)=a(n-1)+n^1 if n odd, a(n)=a(n-1)+ n^0 if n is even.
%C A140144 Equals triangle A177990 * [1,2,3,...]. - _Gary W. Adamson_, May 16 2010
%H A140144 Girtrude Hamm, <a href="https://arxiv.org/abs/2304.03007">Classification of lattice triangles by their two smallest widths</a>, arXiv:2304.03007 [math.CO], 2023.
%H A140144 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,-2,-1,1).
%F A140144 From _R. J. Mathar_, Feb 22 2009: (Start)
%F A140144 a(n) = a(n-1)+2*a(n-2)-2*a(n-3)-a(n-4)+a(n-5).
%F A140144 G.f.: x*(-1-x-x^2+x^3)/ ((1+x)^2*(x-1)^3). (End)
%F A140144 a(n) = Sum_{k=1..n} k^(k mod 2). - _Wesley Ivan Hurt_, Nov 20 2021
%t A140144 a = {}; r = 1; s = 0; Do[k = 0; Do[k = k + (Sin[Pi m/2]^2) m^r + (Cos[Pi m/2]^2) m^s, {m, 1, n}]; AppendTo[a, k], {n, 1, 100}]; a
%Y A140144 Cf. A000027, A000217, A000330, A000537, A000538, A000539, A136047, A140113.
%Y A140144 Cf. A177990. - _Gary W. Adamson_, May 16 2010
%Y A140144 Cf. A002378 (even bisection), A028387 (odd bisection).
%K A140144 nonn,easy
%O A140144 1,2
%A A140144 _Artur Jasinski_, May 12 2008