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 A178377 #6 Sep 08 2022 08:45:53
%S A178377 1,1,-3,-5,-22,-141,719,8765,14319,1707596,-21672017,-962616165,
%T A178377 16392942967,-1419903481091,100267906812546,7990790144939605,
%U A178377 -1147738310571578779,53860607055523082151,-43705893899966302362943
%N A178377 A (-1,-3) Somos-4 sequence associated to y^2 + y = x^3 + 4*x^2 + x.
%C A178377 Hankel transform of the sequence with g.f. 1/(1-x/(1+3x^2/(1+(5/9)x^2/91-(66/25)x^2/(1-...,
%C A178377 where -3,-5/9,66/25,... are the x-coordinates of the multiples of (0,0).
%H A178377 G. C. Greubel, <a href="/A178377/b178377.txt">Table of n, a(n) for n = 0..124</a>
%F A178377 a(n) = (-a(n-1)*a(n-3) - 3*a(n-2)^2)/a(n-4), n>3.
%t A178377 RecurrenceTable[{a[n]==(-a[n-1]*a[n-3] -3*a[n-2]^2)/a[n-4], a[0] == 1, a[1] == 1, a[2] == -3, a[3] == -5}, a, {n, 0, 30}] (* _G. C. Greubel_, Sep 16 2018 *)
%o A178377 (PARI) m=30; v=concat([1,1,-3,-5], vector(m-4)); for(n=5, m, v[n] = ( -v[n-1]*v[n-3] - 3*v[n-2]^2)/v[n-4]); v \\ _G. C. Greubel_, Sep 16 2018
%o A178377 (Magma) I:=[1,1,-3,-5]; [n le 4 select I[n] else (-Self(n-1)*Self(n-3) - 3*Self(n-2)^2)/Self(n-4): n in [1..30]]; // _G. C. Greubel_, Sep 16 2018
%K A178377 easy,sign
%O A178377 0,3
%A A178377 _Paul Barry_, May 26 2010