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 A083319 #9 Jun 13 2015 00:51:02
%S A083319 1,5,21,83,321,1235,4761,18443,71841,281315,1106601,4369403,17304561,
%T A083319 68694995,273202041,1088057963,4337948481,17308878275,69106635081,
%U A083319 276039644123,1102997363601,4408504767155,17623562909721,70462878967883
%N A083319 4^n+3^n-2^n.
%C A083319 Binomial transform of A083318
%H A083319 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (9,-26,24).
%F A083319 a(n)=4^n+3^n-2^n.
%F A083319 G.f. (1-4x+2x^2)/((1-2x)(1-3x)(1-4x)).
%F A083319 E.g.f. exp(4x)+exp(3x)-exp(2x)
%t A083319 CoefficientList[Series[(1-4x+2x^2)/((1-2x)(1-3x)(1-4x)), {x,0,40}],x] (* _Harvey P. Dale_, Mar 28 2011 *)
%Y A083319 Cf. A083320.
%K A083319 easy,nonn
%O A083319 0,2
%A A083319 _Paul Barry_, Apr 25 2003