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 A055820 #20 Sep 08 2022 08:45:01
%S A055820 1,11,24,43,69,103,146,199,263,339,428,531,649,783,934,1103,1291,1499,
%T A055820 1728,1979,2253,2551,2874,3223,3599,4003,4436,4899,5393,5919,6478,
%U A055820 7071,7699,8363,9064,9803,10581,11399,12258
%N A055820 a(n) = T(n,n-3), array T as in A055818.
%H A055820 Vincenzo Librandi, <a href="/A055820/b055820.txt">Table of n, a(n) for n = 3..10000</a>
%H A055820 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (4,-6,4,-1).
%F A055820 a(n) = (n^3 +3*n^2 -10*n -6)/6, for n>3, with a(3) = 1.
%F A055820 From _G. C. Greubel_, Jan 22 2020: (Start)
%F A055820 G.f.: x^3*(1 + 7*x - 14*x^2 + 9*x^3 - 2*x^4)/(1-x)^4.
%F A055820 E.g.f.: (6 +12*x +3*x^2 -2*x^3 - (6 + 6*x - 6*x^2 - x^3)*exp(x))/6. (End)
%p A055820 seq( `if`(n=3, 1, (n^3 +3*n^2 -10*n -6)/6), n=3..50); # _G. C. Greubel_, Jan 22 2020
%t A055820 Join[{1},Table[(n^3+3n^2-10n-6)/6,{n,4,50}]] (* or *) Join[{1},LinearRecurrence[ {4,-6,4,-1},{11,24,43,69},50]] (* _Harvey P. Dale_, Sep 18 2011 *)
%o A055820 (PARI) vector(50, n, my(m=n+2); if(m==3, 1, (m^3 +3*m^2 -10*m -6)/6)) \\ _G. C. Greubel_, Jan 22 2020
%o A055820 (Magma) [1] cat [(n^3 +3*n^2 -10*n -6)/6: n in [4..50]]; // _G. C. Greubel_, Jan 22 2020
%o A055820 (Sage) [1]+[(n^3 +3*n^2 -10*n -6)/6 for n in (4..50)] # _G. C. Greubel_, Jan 22 2020
%o A055820 (GAP) Concatenation([1], List([4..50], n-> (n^3 +3*n^2 -10*n -6)/6)); # _G. C. Greubel_, Jan 22 2020
%Y A055820 Cf. A055818.
%K A055820 nonn,easy
%O A055820 3,2
%A A055820 _Clark Kimberling_, May 28 2000