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 A211435 #13 Oct 23 2022 01:21:37
%S A211435 1,3,5,11,17,25,35,45,59,73,89,107,125,147,169,193,219,245,275,305,
%T A211435 337,371,405,443,481,521,563,605,651,697,745,795,845,899,953,1009,
%U A211435 1067,1125,1187,1249,1313,1379,1445,1515,1585,1657,1731,1805,1883
%N A211435 Number of ordered triples (w,x,y) with all terms in {-n,...,0,...,n} and w+4x+5y=0.
%C A211435 For a guide to related sequences, see A211422.
%F A211435 Conjectures from _Colin Barker_, May 15 2017: (Start)
%F A211435 G.f.: (1 + x + 4*x^3 + x^5 + x^6) / ((1 - x)^3*(1 + x + x^2 + x^3 + x^4)).
%F A211435 a(n) = 2*a(n-1) - a(n-2) + a(n-5) - 2*a(n-6) + a(n-7) for n > 6. (End)
%F A211435 Conjecture: a(n) ~ 4*n^2/5. - _Stefano Spezia_, Oct 17 2022
%t A211435 t[n_] := t[n] = Flatten[Table[w + 4 x + 5 y, {w, -n, n}, {x, -n, n}, {y, -n, n}]]
%t A211435 c[n_] := Count[t[n], 0]
%t A211435 t = Table[c[n], {n, 0, 70}] (* A211435 *)
%t A211435 (t - 1)/2 (* integers *)
%Y A211435 Cf. A211422.
%K A211435 nonn
%O A211435 0,2
%A A211435 _Clark Kimberling_, Apr 11 2012