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 A188895 #53 Feb 16 2025 08:33:14
%S A188895 1,4,96,384,30720,7372800,4335206400,2477260800,25684239974400,
%T A188895 7191587192832000
%N A188895 Number of n X n (real) {-1,1}-matrices having determinant A003433(n).
%H A188895 Minfeng Wang, <a href="/A188895/a188895.txt">C++ program to calculate a(2) .. a(5)</a>
%H A188895 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HadamardsMaximumDeterminantProblem.html">Hadamard's Maximum Determinant Problem</a>
%H A188895 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/-11-Matrix.html">(-1, 1)-Matrix</a>
%F A188895 a(n) = 2^(2n+1) * A051752(n) for n>=2. - _Hugo Pfoertner_ and _Minfeng Wang_, Jan 22 2023
%Y A188895 Cf. A003433, A051752.
%K A188895 nonn,more,hard
%O A188895 0,2
%A A188895 _Eric W. Weisstein_, Apr 19 2011
%E A188895 Offset changed to 0 by _Hugo Pfoertner_, Jan 23 2023
%E A188895 a(5)-a(9) from _Minfeng Wang_, Jan 22 2023