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 A160637 #18 Feb 12 2024 10:07:40
%S A160637 1,1,-2,-8,-32,-128,1024,16384,262144,4194304,-134217728,-8589934592,
%T A160637 -549755813888,-35184372088832,4503599627370496,1152921504606846976,
%U A160637 295147905179352825856,75557863725914323419136,-38685626227668133590597632,-39614081257132168796771975168
%N A160637 Hankel transform of A114464(n+1).
%C A160637 Hankel transform of A114464(n) is A160636.
%C A160637 This is a generalized Somos-4 sequence. - _Michael Somos_, Mar 14 2020
%H A160637 G. C. Greubel, <a href="/A160637/b160637.txt">Table of n, a(n) for n = 0..114</a>
%F A160637 a(n) = (-2)^floor(C(n+1,2)/2) = (-2)^A011848(n+1).
%F A160637 0 = a(n)*a(n+4) - 2*a(n+1)*a(n+3) + 4*a(n+2)^2 = a(n)*a(n+5) - 4*a(n+1)*a(n+4) for all n in Z. - _Michael Somos_, Mar 14 2020
%t A160637 Table[(-2)^Floor[Binomial[n + 1, 2]/2], {n, 0, 50}] (* _G. C. Greubel_, May 03 2018 *)
%t A160637 a[ n_] := (-2)^Quotient[n (n + 1), 4]; (* _Michael Somos_, Mar 14 2020 *)
%o A160637 (PARI) for(n=0, 50, print1((-2)^floor(binomial(n+1,2)/2), ", ")) \\ _G. C. Greubel_, May 03 2018
%o A160637 (Magma) [(-2)^Floor(Binomial(n+1,2)/2): n in [0..50]]; // _G. C. Greubel_, May 03 2018
%Y A160637 Cf. A011848, A114464, A160636.
%K A160637 easy,sign
%O A160637 0,3
%A A160637 _Paul Barry_, May 21 2009