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 A172212 #15 Feb 18 2018 15:01:00
%S A172212 1,12,36,100,233,456,796,1280,1935,2788,3866,5196,6805,8720,10968,
%T A172212 13576,16571,19980,23830,28148,32961,38296,44180,50640,57703,65396,
%U A172212 73746,82780,92525,103008,114256,126296,139155,152860,167438,182916,199321
%N A172212 Number of ways to place 3 nonattacking knights on a 3 X n board.
%H A172212 Vincenzo Librandi, <a href="/A172212/b172212.txt">Table of n, a(n) for n = 1..1000</a>
%H A172212 V. Kotesovec, <a href="https://oeis.org/wiki/User:Vaclav_Kotesovec">Number of ways of placing non-attacking queens and kings on boards of various sizes</a>
%F A172212 a(n) = (9n^3 - 45n^2 + 122n - 144)/2, n>=4.
%F A172212 G.f.: x*(6*x^6-8*x^5+2*x^4+24*x^3-6*x^2+8*x+1)/(x-1)^4. - _Vaclav Kotesovec_, Mar 25 2010
%t A172212 CoefficientList[Series[(6 x^6 - 8 x^5 + 2 x^4 + 24 x^3 - 6 x^2 + 8 x + 1) / (x - 1)^4, {x, 0, 50}], x] (* _Vincenzo Librandi_, May 27 2013 *)
%Y A172212 Cf. A172134, A061989, A047659, A172202.
%K A172212 nonn,easy
%O A172212 1,2
%A A172212 _Vaclav Kotesovec_, Jan 29 2010