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 A086264 #33 Feb 16 2025 08:32:50
%S A086264 1,1,3,84,10020,4851360,9240051240,67745781734400,1883481284085791040
%N A086264 Number of real {0,1} n X n matrices having determinant=1.
%H A086264 Hugo Pfoertner, <a href="http://www.randomwalk.de/sequences/a086264.txt">Determinants of (0,1)-matrices.</a> FORTRAN program.
%H A086264 Minfeng Wang, <a href="/A086264/a086264.cpp.txt">C++ program</a>
%H A086264 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/01-Matrix.html">(0,1)-Matrix</a>.
%H A086264 <a href="/index/Mat#binmat">Index entries for sequences related to binary matrices</a>
%t A086264 a[n_] := Module[{M, iter, cnt = 0}, M = Table[a[i, j], {i, 1, n}, {j, 1, n}]; iter = Thread[{Flatten[M], 0, 1}]; Do[If[Det[M] == 1, cnt++], Evaluate[Sequence @@ iter]]; cnt];
%t A086264 Do[Print[n, " ", a[n]], {n, 1, 4}] (* _Jean-François Alcover_, Dec 09 2018 *)
%Y A086264 Cf. A003024, A003432, A051752, A055165.
%Y A086264 Cf. A046747.
%K A086264 nonn,more
%O A086264 0,3
%A A086264 _Hugo Pfoertner_, Oct 05 2003
%E A086264 a(0)=1 prepended by _Alois P. Heinz_, Jun 18 2022
%E A086264 a(7) from _Minfeng Wang_, Feb 09 2023
%E A086264 a(8) from _Minfeng Wang_, Apr 26 2024