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 A162547 #34 Nov 10 2022 07:40:11
%S A162547 1,0,-4,-16,-64,0,4096,65536,1048576,0,-1073741824,-68719476736,
%T A162547 -4398046511104,0,72057594037927936,18446744073709551616,
%U A162547 4722366482869645213696,0,-1237940039285380274899124224,-1267650600228229401496703205376,-1298074214633706907132624082305024,0
%N A162547 Somos-4 variant: if n!=4k+1, then a(n) = (4*a(n-1)*a(n-3) - 4*a(n-2)^2) / a(n-4), otherwise a(n) = 0, with a(-2) = a(-1) = a(0) = 1.
%C A162547 Hankel transform of A101499.
%C A162547 Hankel transform of A124431. - _Paul Barry_, Oct 02 2009
%H A162547 G. C. Greubel, <a href="/A162547/b162547.txt">Table of n, a(n) for n = 0..114</a>
%H A162547 Paul Barry, <a href="http://arxiv.org/abs/1107.5490">Invariant number triangles, eigentriangles and Somos-4 sequences</a>, arXiv preprint arXiv:1107.5490 [math.CO], 2011.
%H A162547 Paul Barry, <a href="http://dx.doi.org/10.1155/2013/657806">On the Connection Coefficients of the Chebyshev-Boubaker polynomials</a>, The Scientific World Journal, Volume 2013 (2013), Article ID 657806, 10 pages.
%H A162547 Paul Barry, <a href="https://arxiv.org/abs/1912.01126">Riordan arrays, the A-matrix, and Somos 4 sequences</a>, arXiv:1912.01126 [math.CO], 2019.
%F A162547 a(n) = a(-2 - n), a(n) * a(n+5) = 4 * a(n+1) * a(n+4) for all n in Z. - _Michael Somos_, Jul 20 2014
%F A162547 a(4*n + 1) = 0 for all n in Z. - _Michael Somos_, Jun 26 2017
%t A162547 a[ n_] := With[{m = n + 1, k = Quotient[n + 2, 4]}, Boole[Mod[m, 4] != 2] (-1)^k 4^(k (m - 2 k))]; (* _Michael Somos_, Jun 26 2017 *)
%o A162547 (PARI) {a(n) = my(m=n+1, k=(n+2)\4); (m%4!=2) * (-1)^k * 4^(k*(m - 2*k))}; /* _Michael Somos_, Jul 20 2014 */
%Y A162547 Cf. A101499, A124431.
%K A162547 easy,sign
%O A162547 0,3
%A A162547 _Paul Barry_, Jul 05 2009