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 A118992 #8 Jun 17 2025 22:06:39 %S A118992 2,4,32,512,16896,1190144,163899904,46195853312,25585116626944, %T A118992 28281621931343872 %N A118992 Number of real n X n invertible symmetric (+1,-1) matrices. %F A118992 a(n) = 2^(n*(n+1)/2) - A118990(n) = A118994(n) + A118997(n). - _Max Alekseyev_, Jun 12 2025 %Y A118992 Cf. A056990, A086899, A056989, A118990, A118993, A118994, A118997. %K A118992 nonn,more %O A118992 1,1 %A A118992 _Giovanni Resta_, May 08 2006 %E A118992 a(8)-a(10) from _Max Alekseyev_, Jun 17 2025