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 A077831 #11 Feb 28 2025 15:27:12
%S A077831 1,3,11,41,151,557,2055,7581,27967,103173,380615,1404125,5179951,
%T A077831 19109333,70496151,260067021,959412031,3539362437,13057045415,
%U A077831 48168685181,177698871247,655548074933,2418379337655,8921631905325,32912750541151,121418274109413
%N A077831 Expansion of 1/(1-3*x-2*x^2-2*x^3).
%H A077831 Harvey P. Dale, <a href="/A077831/b077831.txt">Table of n, a(n) for n = 0..1000</a>
%H A077831 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,2,2).
%t A077831 CoefficientList[Series[1/(1-3x-2x^2-2x^3),{x,0,30}],x] (* or *) LinearRecurrence[{3,2,2},{1,3,11},30] (* _Harvey P. Dale_, Feb 28 2025 *)
%o A077831 (PARI) Vec(1/(1-3*x-2*x^2-2*x^3)+O(x^99)) \\ _Charles R Greathouse IV_, Sep 27 2012
%Y A077831 Partial sums of S(n, x), for x=1...16, A021823, A000217, A027941, A061278, A089817, A053142, A092521, A076765, A092420, A097784, A097826-A097828, A076139, A097829, A097830.
%K A077831 nonn,easy
%O A077831 0,2
%A A077831 _N. J. A. Sloane_, Nov 17 2002