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 A167617 #17 Oct 08 2024 22:19:04
%S A167617 0,0,3,-6,10,-21,42,-84,171,-342,682,-1365,2730,-5460,10923,-21846,
%T A167617 43690,-87381,174762,-349524,699051,-1398102,2796202,-5592405,
%U A167617 11184810,-22369620,44739243,-89478486,178956970,-357913941,715827882,-1431655764,2863311531
%N A167617 G.f.: x^2*(3+3*x+x^2) / ( (2*x+1) * (1+x) * (1+x+x^2) * (x^2-x+1) ) .
%C A167617 The derived sequence a(n+1) + 2*a(n) reads 0,3,0,-2,-1,0 (and repeat with period 6).
%H A167617 G. C. Greubel, <a href="/A167617/b167617.txt">Table of n, a(n) for n = 0..1000</a>
%H A167617 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (-3, -3, -3, -3, -3, -2).
%F A167617 a(3*k+2) + a(3*k+3) + a(3*k+4) = (-1)^(k+1)*A024088(k+1).
%F A167617 a(n) = (-1)^n*A024495(n+1) + A131531(n+1).
%F A167617 a(n) = -3*a(n-1) -3*a(n-2) -3*a(n-3) -3*a(n-4) -3*a(n-5) -2*a(n-6).
%t A167617 CoefficientList[Series[x^2(3+3x+x^2)/((2x+1)(1+x)(1+x+x^2)(x^2-x+1)), {x,0,40}],x] (* or *) LinearRecurrence[{-3,-3,-3,-3,-3,-2},{0,0,3,-6,10,-21},40] (* _Harvey P. Dale_, Sep 08 2011 *)
%Y A167617 Cf. A167613.
%K A167617 sign,easy
%O A167617 0,3
%A A167617 _Paul Curtz_, Nov 07 2009
%E A167617 Edited and extended by _R. J. Mathar_, Nov 12 2009