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%I #8 Mar 23 2024 20:23:32
%S 0,-1,-2,0,0,-128,-1024,0,0,-4194304,-134217728,0,0,-35184372088832,
%T -4503599627370496,0,0,-75557863725914323419136,
%U -38685626227668133590597632,0,0,-41538374868278621028243970633760768,-85070591730234615865843651857942052864,0
%N Imaginary part of a (-4,-4) Gaussian integer Somos-4 sequence.
%C Imaginary part of the Hankel transform of A183893(n) + I*A183894(n).
%C A183895(n) + I*a(n) is a (-4,-4) Gaussian integer Somos-4 sequence.
%H G. C. Greubel, <a href="/A183896/b183896.txt">Table of n, a(n) for n = 0..112</a>
%F a(n) = mod(binomial(n+1,2), 2)*A183895(n).
%t Table[((-1)^Floor[(n+1)/2] -1)*2^(Floor[n*(n+1)/4] -1), {n,0,30}] (* _G. C. Greubel_, Mar 23 2024 *)
%o (Magma) [((-1)^Floor((n+1)/2) -1)*2^Floor((n^2+n-4)/4): n in [0..30]]; // _G. C. Greubel_, Mar 23 2024
%o (SageMath) [((-1)^((n+1)//2) -1)*2^(n*(n+1)//4 -1) for n in range(31)] # _G. C. Greubel_, Mar 23 2024
%Y Cf. A183893, A183894, A183895.
%K sign
%O 0,3
%A _Paul Barry_, Jan 07 2011
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