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 A027470 #28 Sep 08 2022 08:44:49
%S A027470 225,675,1350,2250,3375,4725,6300,8100,10125,12375,14850,17550,20475,
%T A027470 23625,27000,30600,34425,38475,42750,47250,51975,56925,62100,67500,
%U A027470 73125,78975,85050,91350,97875,104625,111600,118800,126225
%N A027470 a(n) = 225*(n-1)*(n-2)/2.
%H A027470 Vincenzo Librandi, <a href="/A027470/b027470.txt">Table of n, a(n) for n = 3..1000</a>
%H A027470 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A027470 Numerators of sequence a[n,n-2] in (a[i,j])^4 where a[i,j] = binomial(i-1, j-1)/2^(i-1) if j<=i, 0 if j>i.
%F A027470 G.f.: 225*(1 - 3*x + 3*x^2)/(1 - x)^3. - _Vincenzo Librandi_, Dec 29 2012
%F A027470 a(3)=225, a(4)=675, a(5)=1350, a(n) = 3*a(n-1) -3*a(n-2) +a(n-3). - _Harvey P. Dale_, Feb 01 2013
%p A027470 seq(225*binomial(n-1,2), n=3..50); # _G. C. Greubel_, May 14 2021
%t A027470 Table[225 (n-1) (n-2)/2, {n, 3, 50}] (* _Vincenzo Librandi_, Dec 29 2012 *)
%t A027470 LinearRecurrence[{3,-3,1},{225,675,1350},40] (* _Harvey P. Dale_, Feb 01 2013 *)
%o A027470 (Magma) [225*(n-1)*(n-2)/2: n in [3..50]]; // _Vincenzo Librandi_, Dec 29 2012
%o A027470 (PARI) a(n)=225*(n-1)*(n-2)/2 \\ _Charles R Greathouse IV_, Jun 17 2017
%o A027470 (Sage) [225*binomial(n-1,2) for n in (3..50)] # _G. C. Greubel_, May 14 2021
%Y A027470 Third diagonal of A027467.
%K A027470 nonn,easy
%O A027470 3,1
%A A027470 _Olivier Gérard_