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 A317188 #24 Oct 15 2021 16:57:39
%S A317188 1,3,8,18,39,85,189,422,942,2099,4673,10400,23148,51528,114709,255359,
%T A317188 568460,1265450,2817015,6270953,13959773,31075874,69178058,153997383,
%U A317188 342813793,763138256,1698823128,3781752544,8418564665,18740578667,41718428560,92869452514
%N A317188 a(n) = 1 + 2 * (a(n-1) + a(n-4) + a(n-6)) + a(n-7) for n>3, with initial values 0 if n<0, and 1,3,8,18 for n=0..3.
%C A317188 Some mail programs automatically include copies of all earlier messages in the same thread. In some cases (especially when rich text format is used) any unrecognized character is replaced by two copies of itself, leading to exponential growth.
%C A317188 The present sequence illustrates this growth for UTF-8 encoding and the CP1252 character set, for the single code point 150.
%D A317188 Fred Lunnon and Tomas Rokicki, Posting to Math Fun Mailing List, circa Jul 25 2018
%H A317188 Harvey P. Dale, <a href="/A317188/b317188.txt">Table of n, a(n) for n = 0..1000</a>
%H A317188 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (3,-2,0,2,-2,2,-1,-1).
%F A317188 G.f.: -(x^4-x^2-1)/((x-1)*(x+1)*(x^6+x^5-x^4+3*x^3-3*x^2+3*x-1)). - _Alois P. Heinz_, Jul 28 2018
%t A317188 LinearRecurrence[{3,-2,0,2,-2,2,-1,-1},{1,3,8,18,39,85,189,422},40] (* _Harvey P. Dale_, Oct 15 2021 *)
%K A317188 nonn,easy
%O A317188 0,2
%A A317188 _Tomas Rokicki_, Jul 28 2018
%E A317188 More terms from _Altug Alkan_, Jul 28 2018