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 A099462 #12 Sep 08 2022 08:45:15
%S A099462 0,1,0,4,4,16,32,80,192,448,1088,2560,6144,14592,34816,82944,197632,
%T A099462 471040,1122304,2674688,6373376,15187968,36192256,86245376,205520896,
%U A099462 489750528,1167065088,2781085696,6627262464,15792603136,37633392640
%N A099462 Expansion of x/(1 - 4*x^2 - 4*x^3).
%C A099462 Binomial transform is A099463.
%H A099462 G. C. Greubel, <a href="/A099462/b099462.txt">Table of n, a(n) for n = 0..1000</a>
%H A099462 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (0,4,4).
%F A099462 a(n) = 4*a(n-2) + 4*a(n-3).
%F A099462 a(n) = Sum_{k=0..floor((n-1)/2)} binomial(k, n-2*k-1)*4^k.
%F A099462 a(n+1) = Sum_{k=0..floor(n/2)} C((n-k)/2, k)*(1+(-1)^(n-k))*2^(n-k). - _Paul Barry_, Sep 09 2005
%t A099462 LinearRecurrence[{0,4,4}, {0,1,0}, 40] (* _G. C. Greubel_, Nov 18 2021 *)
%o A099462 (Magma) [n le 3 select (1+(-1)^n)/2 else 4*(Self(n-2) +Self(n-3)): n in [1..41]]; // _G. C. Greubel_, Nov 18 2021
%o A099462 (Sage)
%o A099462 def a(n): return sum( 4^k*binomial(k, n-2*k-1) for k in (0..(n-1)//2) )
%o A099462 [a(n) for n in (0..40)] # _G. C. Greubel_, Nov 18 2021
%Y A099462 Cf. A099463.
%K A099462 easy,nonn
%O A099462 0,4
%A A099462 _Paul Barry_, Oct 16 2004