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 A165904 #8 Sep 08 2022 08:45:48
%S A165904 1,2,4,8,32,96,448,2944,15104,160768,1565696,16812032,341250048,
%T A165904 5081473024,128940408832,4153114198016,110562817540096,
%U A165904 6199850375708672,294499013825921024,17095312584100282368,1743063839902067064832
%N A165904 Somos-4 recurrence with a(i)=2^i for 0<=i<=3.
%H A165904 G. C. Greubel, <a href="/A165904/b165904.txt">Table of n, a(n) for n = 0..148</a>
%F A165904 a(n) = 2^n*A006720(n).
%F A165904 a(n) = (a(n-1)*a(n-3) + a(n-2)^2)/a(n-4). - _G. C. Greubel_, Sep 18 2018
%t A165904 RecurrenceTable[{a[n] == (a[n-1]*a[n-3] +a[n-2]^2)/a[n-4], a[0] == 1, a[1] == 2, a[2] == 4, a[3] == 8}, a, {n, 0, 30}] (* _G. C. Greubel_, Sep 18 2018 *)
%o A165904 (PARI) a(n)=if(n<4,[1,2,4,8][n+1],(a(n-1)*a(n-3)+a(n-2)^2)/a(n-4))
%o A165904 (Magma) I:=[1,2,4,8]; [n le 4 select I[n] else (Self(n-1)*Self(n-3) + Self(n-2)^2)/Self(n-4): n in [1..30]]; // _G. C. Greubel_, Sep 18 2018
%Y A165904 Cf. A006720, A157005.
%K A165904 nonn
%O A165904 0,2
%A A165904 _Jaume Oliver Lafont_, Sep 29 2009
%E A165904 "frac" keyword removed by _Jaume Oliver Lafont_, Oct 13 2009