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 A077930 #23 Jun 13 2015 00:50:48
%S A077930 1,-1,2,-3,6,-10,18,-31,55,-96,169,-296,520,-912,1601,-2809,4930,
%T A077930 -8651,15182,-26642,46754,-82047,143983,-252672,443409,-778128,
%U A077930 1365520,-2396320,4205249,-7379697,12950466,-22726483,39882198,-69988378,122821042,-215535903,378239143,-663763424
%N A077930 Expansion of (1-x)^(-1)/(1+2*x+x^2+x^3).
%C A077930 Signed version of A060945: a(n) = (-1)^n * A060945(n).
%H A077930 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (-1,1,0,1).
%F A077930 a(n+1)-a(n) = (-1)^(n+1)*A005314(n+2). - R. J. Mathar, Mar 14 2011
%F A077930 a(0)=1, a(1)=-1, a(2)=2, a(3)=-3, a(n)=-a(n-1)+a(n-2)+a(n-4). - _Harvey P. Dale_, Feb 20 2013
%t A077930 CoefficientList[Series[1/(1-x)/(1+2x+x^2+x^3),{x,0,50}],x] (* or *) LinearRecurrence[ {-1,1,0,1},{1,-1,2,-3},50] (* _Harvey P. Dale_, Feb 20 2013 *)
%o A077930 (PARI) Vec((1-x)^(-1)/(1+2*x+x^2+x^3)+O(x^99)) \\ _Charles R Greathouse IV_, Sep 24 2012
%Y A077930 All of A060945, A077930, A181532 are variations of the same sequence. - _N. J. A. Sloane_, Mar 04 2012
%K A077930 sign,easy
%O A077930 0,3
%A A077930 _N. J. A. Sloane_, Nov 17 2002