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 A201222 #16 Sep 12 2015 11:00:27
%S A201222 3,9,18,81,123,324,843,2401,5778,15129,39603,104976,271443,710649,
%T A201222 1860498,4879681,12752043,33385284,87403803,228886641,599074578,
%U A201222 1568397609,4106118243,10750371856,28143753123,73681302249,192900153618,505022001201,1322157322203
%N A201222 Number of ways to place k non-attacking knights on a 2 X n horizontal cylinder, summed over all k>=0.
%H A201222 Vincenzo Librandi, <a href="/A201222/b201222.txt">Table of n, a(n) for n = 1..1000</a>
%H A201222 V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Non-attacking chess pieces</a>
%t A201222 Table[If[Mod[n,4]==0,LucasL[n/2]^4,LucasL[2n]+1+(-1)^n],{n,1,50}]
%Y A201222 Cf. A189145, A001333, A051927, A006506, A067966.
%K A201222 nonn,easy
%O A201222 1,1
%A A201222 _Vaclav Kotesovec_, Nov 28 2011