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 A172139 #16 Apr 19 2022 04:38:55
%S A172139 0,1,126,1168,7334,35749,137970,438984,1208246,2969389,6662480,
%T A172139 13873100,27144408,50389581,89424014,152638280,251834530,403250693,
%U A172139 628798516,957543164,1427453780,2087456085,2999819778,4242915176
%N A172139 Number of ways to place 4 nonattacking zebras on an n X n board.
%C A172139 Zebra is a (fairy chess) leaper [2,3].
%H A172139 Vincenzo Librandi, <a href="/A172139/b172139.txt">Table of n, a(n) for n = 1..1000</a>
%H A172139 Vaclav 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>
%H A172139 <a href="/index/Rec#order_09">Index entries for linear recurrences with constant coefficients</a>, signature (9,-36,84,-126,126,-84,36,-9,1).
%F A172139 a(n) = (n^8 - 54*n^6 + 240*n^5 + 827*n^4 - 8592*n^3 + 10362*n^2 + 75600*n - 204864)/24, n >= 9.
%F A172139 G.f.: x^2*(1 + 117*x + 70*x^2 + 1274*x^3 + 1333*x^4 - 2109*x^5 - 462*x^6 + 8858*x^7 - 17006*x^8 + 15166*x^9 - 6838*x^10 + 1478*x^11 - 650*x^12 + 760*x^13 - 376*x^14 + 64*x^15)/(1-x)^9. - _Vaclav Kotesovec_, Mar 25 2010
%t A172139 CoefficientList[Series[x(1+117*x+70*x^2+1274*x^3+1333*x^4-2109*x^5-462*x^6 +8858*x^7-17006*x^8+15166*x^9-6838*x^10+1478*x^11-650*x^12+760*x^13-376*x^14 +64*x^15)/(1-x)^9, {x,0,40}], x] (* _Vincenzo Librandi_, May 27 2013 *)
%o A172139 (SageMath) [0,1,126,1168,7334,35749,137970,438984] + [(n^8 -54*n^6 +240*n^5 +827*n^4 -8592*n^3 +10362*n^2 +75600*n -204864)/24 for n in (9..50)] # _G. C. Greubel_, Apr 19 2022
%Y A172139 Cf. A061994, A172127, A172135, A172137, A172138.
%K A172139 nonn
%O A172139 1,3
%A A172139 _Vaclav Kotesovec_, Jan 26 2010