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 A178077 #8 Sep 08 2022 08:45:53
%S A178077 1,2,4,-16,-256,-3072,-81920,-524288,184549376,20401094656,
%T A178077 3848290697216,932385860354048,-229683580995895296,
%U A178077 -514202991054653751296,-608004684669466821263360,-1669526556887802890269229056,-2074787505842297340730932199424,33552176086840775798814740439891968
%N A178077 A (4,-8) Somos-4 sequence.
%C A178077 Hankel transform of A178076.
%H A178077 G. C. Greubel, <a href="/A178077/b178077.txt">Table of n, a(n) for n = 0..94</a>
%F A178077 a(n) = (4*a(n-1)*a(n-3) - 8*a(n-2)^2)/a(n-4), n>=4.
%t A178077 RecurrenceTable[{a[n] == (4*a[n-1]*a[n-3] -8*a[n-2]^2)/a[n-4], a[0] == 1, a[1] == 2, a[2] == 4, a[3] == -16}, a, {n, 0, 30}] (* _G. C. Greubel_, Sep 18 2018 *)
%o A178077 (PARI) m=30; v=concat([1,2,4,-16], vector(m-4)); for(n=5, m, v[n] = ( 4*v[n-1]*v[n-3] -8*v[n-2]^2)/v[n-4]); v \\ _G. C. Greubel_, Sep 18 2018
%o A178077 (Magma) I:=[1,2,4,-16]; [n le 4 select I[n] else (4*Self(n-1)*Self(n-3) - 8*Self(n-2)^2)/Self(n-4): n in [1..30]]; // _G. C. Greubel_, Sep 18 2018
%K A178077 easy,sign
%O A178077 0,2
%A A178077 _Paul Barry_, May 19 2010
%E A178077 More terms from _G. C. Greubel_, Sep 18 2018