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 A093378 #12 Jan 30 2023 07:39:52 %S A093378 2,12,22,168,1558,5148,8062,177072,860882,738492,121008888,298775878, %T A093378 1232566932,14864798542,58374617952 %N A093378 a(n) = numerator of any non-diagonal entry of the matrix A^n, where A is described in the Comments lines. %C A093378 A = %C A093378 [ -3/5 -(2/5)i, -(2/5)i, -(2/5)i, -(2/5)i ] %C A093378 [ -(2/5)i, -3/5 +(2/5)i, -(2/5)i, (2/5)i ] %C A093378 [ -(2/5)i, -(2/5)i, -3/5 +(2/5)i, (2/5)i ] %C A093378 [ -(2/5)i, (2/5)i, (2/5)i, -3/5 -(2/5)i ] %C A093378 is the Cayley transform of the matrix iH, where H = %C A093378 [1, 1, 1, 1] %C A093378 [1, -1, 1, -1] %C A093378 [1, 1, -1, -1] %C A093378 [1, -1, -1, 1] %C A093378 is a Hadamard matrix of order 4 and i is the imaginary unit. %Y A093378 Cf. A066771. %K A093378 nonn,frac,more %O A093378 1,1 %A A093378 _Simone Severini_, Apr 28 2004