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 A137531 #25 Feb 17 2017 14:21:23
%S A137531 1,4,10,23,53,123,286,665,1546,3594,8355,19423,45153,104968,244021,
%T A137531 567280,1318766,3065759,7127025,16568323,38516678,89540413,208156206,
%U A137531 483904470,1124941411,2615171499,6079536145,14133206848,32855719753,76380281708,177562612466
%N A137531 a(n) = 3*a(n-1) - 2*a(n-2) + a(n-3).
%H A137531 G. C. Greubel, <a href="/A137531/b137531.txt">Table of n, a(n) for n = 0..1000</a>
%H A137531 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-2,1).
%F A137531 G.f.: (1 + x) / (1 - 3*x + 2*x^2 - x^3). - _Colin Barker_, Feb 17 2017
%t A137531 LinearRecurrence[{3, -2, 1}, {1, 4, 10}, 100] (* _G. C. Greubel_, Feb 17 2017 *)
%o A137531 (PARI) a=[1,4,10];for(i=1,99,a=concat(a,3*a[#a]-2*a[#a-1]+a[#a-2]));a \\ _Charles R Greathouse IV_, Jun 01 2011
%o A137531 (PARI) Vec((1 + x) / (1 - 3*x + 2*x^2 - x^3) + O(x^40)) \\ _Colin Barker_, Feb 17 2017
%Y A137531 Cf. A159347, A097550.
%K A137531 nonn,easy
%O A137531 0,2
%A A137531 _Paul Curtz_, Apr 25 2008
%E A137531 More terms from _Vladimir Joseph Stephan Orlovsky_, Jan 20 2009