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 A002634 M0397 N0153 #22 Jan 11 2018 01:09:03 %S A002634 -2,3,0,25,152,1350,12644,131391,1489568,18329481,243365514, %T A002634 3468969962,52848096274,857073295427,14744289690560,268202790690465, %U A002634 5143861702523924,103746422699053582,2195275169113687656,48629604864202585247 %N A002634 From discordant permutations. %D A002634 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). %D A002634 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). %H A002634 K. Yamamoto, <a href="https://www.jstage.jst.go.jp/article/kyushumfs/10/1/10_1_1/_pdf">Structure polynomial of Latin rectangles and its application to a combinatorial problem</a>, Memoirs of the Faculty of Science, Kyusyu University, Series A, 10 (1956), 1-13, DOI: 10.2206/kyushumfs.10.1 %H A002634 K. Yamamoto, <a href="/A000183/a000183.pdf">Structure polynomial of Latin rectangles and its application to a combinatorial problem</a>, Memoirs of the Faculty of Science, Kyusyu University, Series A, 10 (1956), 1-13. [Annotated scanned copy] %F A002634 a(n) = b(n) - 2*b(n-1) + b(n-2) + 2*a(n-1) + 2*a(n-2) - 2*a(n-3) + a(n-4) + 4*(-1)^n where b(n) = A000183(n) and n>6. a(3)=-2, a(4)=3, a(5)=0, a(6)=25. - _Sean A. Irvine_, May 03 2014 %Y A002634 Cf. A000183. %K A002634 sign %O A002634 3,1 %A A002634 _N. J. A. Sloane_ %E A002634 More terms from _Sean A. Irvine_, May 03 2014