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 A386226 #16 Jul 16 2025 23:39:34
%S A386226 1,4,10,16,27,34,44,54,69,76,86,96,111,118,128,138,153,160,170,180,
%T A386226 195,202,212,222,237,244,254,264,279,286,296,306,321,328,338,348,363,
%U A386226 370,380,390,405,412,422,432,447,454,464,474,489,496,506,516,531,538,548
%N A386226 The maximum possible number of 8-cycles in an outerplanar graph on n vertices.
%C A386226 For n >= 12, the first differences are 4-periodic: 7,10,10,15,7,10,10,15,...
%H A386226 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,0,1,-1).
%F A386226 a(n) = 10*n - 99 + 5*floor(n/4) - 3*floor((n+3)/4) for n >= 12.
%F A386226 a(n) ~ (21/2)*n.
%F A386226 G.f.: x^8*(4*x^8+4*x^7+4*x^6+4*x^5+10*x^4+6*x^3+6*x^2+3*x+1)/((x+1)*(x^2+1)*(x-1)^2). - _Alois P. Heinz_, Jul 15 2025
%t A386226 Drop[CoefficientList[Series[x^8*(4*x^8+4*x^7+4*x^6+4*x^5+10*x^4+6*x^3+6*x^2+3*x+1)/((x+1)*(x^2+1)*(x-1)^2),{x,0,62}],x],8] (* _James C. McMahon_, Jul 16 2025 *)
%K A386226 nonn,easy
%O A386226 8,2
%A A386226 _Stephen Bartell_, Jul 15 2025