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 A054121 #12 Oct 19 2022 08:10:06
%S A054121 1,9,39,114,261,507,879,1404,2109,3021,4167,5574,7269,9279,11631,
%T A054121 14352,17469,21009,24999,29466,34437,39939,45999,52644,59901,67797,
%U A054121 76359,85614,95589,106311,117807,130104,143229,157209
%N A054121 T(n,n-3), array T as in A054120.
%H A054121 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-6,4,-1)
%F A054121 For n>3, a(n) = 3/2 * (3n^3-30n^2+107n-134).
%t A054121 LinearRecurrence[{4,-6,4,-1},{1,9,39,114,261},40] (* _Harvey P. Dale_, Sep 28 2017 *)
%o A054121 (PARI) a(n)=max(9*n^3-90*n^2+321*n-402,2)/2 \\ _Charles R Greathouse IV_, Oct 19 2022
%K A054121 nonn,easy
%O A054121 3,2
%A A054121 _Clark Kimberling_