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 A113679 #22 Oct 02 2023 10:36:59
%S A113679 1,0,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,
%T A113679 -2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,
%U A113679 -2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2,-2
%N A113679 Expansion of (1-x-2x^2)/(1-x).
%C A113679 From _Gary W. Adamson_, Mar 06 2012: (Start)
%C A113679 Signed (1, 0, -2, 2, -2, 2, ...) and convolved with the Toothpick sequence A139250 = A151548: (1, 3, 5, 7, 5, 11, ...). The inverse of (1, 0, -2, 2, -2, ...) = A151575: (1, 0, 2, -2, 6, -10, 22, ...).
%C A113679 The unsigned sequence convolved with:
%C A113679 (1, 2, 3, ...) = A002523, (n^2 + 1). Convolved with:
%C A113679 (A001045) = .... A097064: (1, 1, 5, 9, 21, 41, ...).
%C A113679 (End)
%H A113679 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (1).
%F A113679 a(n) = C(0, n) + 2*C(1, n) - 2.
%t A113679 CoefficientList[Series[(1-x-2x^2)/(1-x),{x,0,80}],x] (* or *) Join[{1,0}, PadRight[{},80,-2]] (* _Harvey P. Dale_, Mar 05 2012 *)
%Y A113679 Cf. A113680.
%Y A113679 Cf. A139250, A151548, A151575, A002523. - _Gary W. Adamson_, Mar 06 2012
%K A113679 easy,sign
%O A113679 0,3
%A A113679 _Paul Barry_, Nov 04 2005