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 A036981 #26 Jul 19 2025 04:49:05 %S A036981 1,6,720,31449600,444733651353600,10070314878246926155776000, %T A036981 614972203951464612786852376432607232000 %N A036981 Number of (2n+1) X (2n+1) symmetric matrices each of whose rows is a permutation of 1..(2n+1). %C A036981 Number of different schedules for 2n+2 teams. - Andres Cardemil (andrescarde(AT)yahoo.com), Nov 28 2001 %H A036981 Minjia Shi, Li Xu, and Denis S. Krotov, <a href="https://arxiv.org/abs/1806.00009">The number of the non-full-rank Steiner triple systems</a>, arXiv:1806.00009 [math.CO], 2018-2021. %H A036981 <a href="/index/To#tournament">Index entries for sequences related to tournaments</a>. %F A036981 a(n) = A000438(n+1) * (2*n+1)!. %Y A036981 Cf. A000438, A000474, A035481, A036980, A064120, A065594. %K A036981 nonn,more %O A036981 0,2 %A A036981 _Joshua Zucker_ and Joe Keane %E A036981 a(5)-a(6) computed from A000438 by _Max Alekseyev_, Jun 17 2011