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 A091471 #15 Feb 16 2025 08:32:52
%S A091471 2,12,464,50224,25095232
%N A091471 Number of n X n matrices with entries {-1,1} that are diagonalizable over the complex numbers.
%C A091471 See A091472 for definition of diagonalizable and for Mathematica definitions.
%H A091471 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/DiagonalizableMatrix.html">Diagonalizable Matrix</a>
%H A091471 <a href="/index/Mat#binmat">Index entries for sequences related to binary matrices</a>
%t A091471 Table[Count[Matrices[n, {-1, 1}], _?DiagonalizableQ], {n, 4}]
%o A091471 (Sage)
%o A091471 import itertools
%o A091471 def a(n):
%o A091471 ans, W = 0, itertools.product([-1, 1], repeat=n*n)
%o A091471 for w in W:
%o A091471 if Matrix(QQbar, n, n, w).is_diagonalizable(): ans += 1
%o A091471 return ans # _Robin Visser_, Sep 27 2023
%Y A091471 Cf. A091470, A091472.
%K A091471 nonn,more
%O A091471 1,1
%A A091471 _Eric W. Weisstein_, Jan 12 2004
%E A091471 a(5) from _Robin Visser_, Sep 27 2023