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 A011897 #33 Aug 15 2025 07:35:16
%S A011897 0,0,0,0,1,4,8,14,22,33,48,66,88,114,145,182,224,272,326,387,456,532,
%T A011897 616,708,809,920,1040,1170,1310,1461,1624,1798,1984,2182,2393,2618,
%U A011897 2856,3108,3374,3655,3952,4264,4592,4936,5297,5676,6072,6486,6918,7369,7840
%N A011897 a(n) = floor(n*(n-1)*(n-2)/15).
%H A011897 Vincenzo Librandi, <a href="/A011897/b011897.txt">Table of n, a(n) for n = 0..1000</a>
%H A011897 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1,0,1,-3,3,-1).
%F A011897 From _R. J. Mathar_, Apr 15 2010: (Start)
%F A011897 a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) + a(n-5) - 3*a(n-6) + 3*a(n-7) - a(n-8).
%F A011897 G.f.: x^4*(1+x-x^2+x^3) / ( (1-x)^4*(1+x+x^2+x^3+x^4) ). (End)
%t A011897 CoefficientList[Series[x^4(1+x-x^2+x^3)/((1-x)^3*(1-x^5)),{x,0,45}],x] (* _Harvey P. Dale_, Feb 25 2011 *)
%t A011897 Floor[2*Binomial[Range[0, 50], 3]/5] (* _G. C. Greubel_, Oct 16 2024 *)
%o A011897 (Magma) [Floor(n*(n-1)*(n-2)/15): n in [0..50]]; // _Vincenzo Librandi_, Jul 07 2012
%o A011897 (SageMath) [2*binomial(n,3)//5 for n in range(51)] # _G. C. Greubel_, Oct 16 2024
%Y A011897 Cf. A011886.
%K A011897 nonn,easy
%O A011897 0,6
%A A011897 _N. J. A. Sloane_