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 A097625 #9 Aug 08 2015 20:32:30
%S A097625 -1,0,2,-4,8,0,80,544,5248,53504,601344,7339520,96797696,1371889664,
%T A097625 20797212672,335835828224,5755617771520,104346351861760,
%U A097625 1995288143593472,40135085601325056,847203499270995968
%N A097625 a(n) = Sum_{k=0..n} (-2)^k * binomial(2n-k,k) * (n-k)!.
%C A097625 Permanent of certain n X 2 Toeplitz-(1,-1) matrices.
%H A097625 A. R. Kräuter, <a href="http://www.mat.univie.ac.at/~slc/opapers/s11kraeu.html">Über die Permanente gewisser zirkulärer Matrizen...</a>, Sem. Loth. Combin. B11b (1984) 82-94
%p A097625 A097625 := proc(n) add((-2)^k*(n-k)!*binomial(2*n-k,k),k=0..n) ; end proc:
%p A097625 seq(A097625(n),n=1..30) ; # _R. J. Mathar_, Sep 18 2011
%Y A097625 Cf. A000271.
%K A097625 sign
%O A097625 1,3
%A A097625 _Ralf Stephan_, Sep 20 2004