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 A007683 M2289 #14 Jan 10 2018 03:12:00
%S A007683 1,-3,3,9,21,-33,-1173,-13515,-113739,-532209,6284379,264830061,
%T A007683 5897799141,104393462439,1459983940203,10308316834293,
%U A007683 -308010522508395,-19576840707893409,-726806556195360069,-22261372611370303875,-591210850189999983099
%N A007683 a(1) = 1; a(n) = -Sum_{k = 1..n-1} (n+k)!a(k)/(2k)!.
%D A007683 H. W. Gould, A class of binomial sums and a series transform, Utilitas Math., 45 (1994), 71-83.
%D A007683 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A007683 H. W. Gould, <a href="/A007680/a007680.pdf">A class of binomial sums and a series transform</a>, Utilitas Math., 45 (1994), 71-83. (Annotated scanned copy)
%Y A007683 Cf. A067000.
%K A007683 sign
%O A007683 1,2
%A A007683 _N. J. A. Sloane_