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 A269917 #20 Mar 15 2025 09:21:16
%S A269917 1,5,21,81,297,1052,3635,12333,41255,136449,447147,1454091,4697983,
%T A269917 15094393,48264551,153678185,487510286,1541427097,4859385039,
%U A269917 15278735029,47923821239,149992151725,468512665975,1460770946689,4546890238683,14131055304241,43854326838403
%N A269917 Number of ternary strings of length n with maximal run length five containing 111112.
%H A269917 <a href="http://math.stackexchange.com/questions/1685843">Words built with 0,1,2</a>
%H A269917 Marko Riedel, <a href="/A269917/a269917.maple.txt">Maple code by total enumeration and by generating function.</a>
%H A269917 <a href="/index/Rec#order_15">Index entries for linear recurrences with constant coefficients</a>, signature (3,3,-1,-9,-21,-41,-59,-69,-71,-65,-50,-32,-18,-8,-2).
%F A269917 G.f.: x^6*(x+1)*(x^2+x+1)*(x^2-x+1)*(x^4+x^3+x^2+x+1) / ((2*x^5+2*x^4 +2*x^3 +2*x^2+2*x-1) * (x^10+3*x^9+5*x^8+7*x^7+9*x^6+9*x^5 +7*x^4 +5*x^3 +3*x^2+x-1)).
%t A269917 Drop[CoefficientList[Series[x^6 (x + 1) (x^2 + x + 1) (x^2 - x + 1) (x^4 + x^3 + x^2 + x + 1)/((2 x^5 + 2 x^4 + 2 x^3 + 2 x^2 + 2 x - 1) (x^10 + 3 x^9 + 5 x^8 + 7 x^7 + 9 x^6 + 9 x^5 + 7 x^4 + 5 x^3 + 3 x^2 + x - 1)), {x, 0, 32}], x], 6] (* _Michael De Vlieger_, Mar 08 2016 *)
%Y A269917 Cf. A081038, A269914, A269915, A269916.
%K A269917 nonn
%O A269917 6,2
%A A269917 _Marko Riedel_, Mar 07 2016