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 A181685 #19 Jul 04 2019 10:47:53
%S A181685 0,36,432,1296,15552,139968,559872,5038848,40310784,181398528,
%T A181685 1451188224,10883911680,52242776064,391820820480,2821109907456,
%U A181685 14105549537280,101559956668416,710919696678912,3656158440062976,25593109080440832,175495605123022848,921351926895869952
%N A181685 Expansion of 36*x^2*(1+6*x-36*x^2) / ( (1-6*x)^2 *(1+6*x+36*x^2) ).
%C A181685 The old definition was: Colorless combinations of quarks and antiquarks of length n >= 1.
%D A181685 Florentin Smarandache, "Matter, Antimatter and Unmatter", Infinite Energy, Concord, NH, USA, Vol. 11, Issue 62, 50-51, 2005.
%H A181685 Florentin Smarandache, <a href="http://cdsweb.cern.ch/record/798551/files/ext-2004-142.pdf?version=1">A New Form of Matter - Unmatter, Formed by Particles and Anti-Particles"</a>, EXT-2004-182 in CERN's web site, 2004.
%H A181685 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (6,0,216,-1296).
%F A181685 a(n) = ( n - 1 - 2*floor((n-1)/3) )*6^n.
%t A181685 Table[(n - 1 - 2 Floor[(n - 1)/3]) 6^n, {n, 1, 30}]
%t A181685 LinearRecurrence[{6,0,216,-1296},{0,36,432,1296},30] (* _Harvey P. Dale_, Jul 04 2019 *)
%o A181685 (PARI) concat(0, 36*Vec(x*(1+6*x-36*x^2) / (1-6*x)^2 / (1+6*x+36*x^2)+O(x^99)))
%K A181685 nonn,easy
%O A181685 1,2
%A A181685 Florentin Smarandache (smarand(AT)unm.edu), Nov 04 2010
%E A181685 Entry revised by Editors of the OEIS, Sep 11 2014