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 A082413 #13 Sep 09 2018 04:08:56 %S A082413 1,7,57,495,4401,39447,354537,3189375,28700001,258286887,2324542617, %T A082413 20920765455,188286534801,1694577750327,15251196564297, %U A082413 137260759512735,1235346806916801,11118121176157767,100063090327139577,900567812169415215 %N A082413 a(n) = (2*9^n + 3^n)/3. %C A082413 Binomial transform of A082412. %H A082413 Nathaniel Johnston, <a href="/A082413/b082413.txt">Table of n, a(n) for n = 0..250</a> %H A082413 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (12,-27). %F A082413 G.f.: (1-5*x)/((1-3*x)*(1-9*x)); %F A082413 E.g.f.: (2*exp(9*x) + exp(3*x))/3. %F A082413 a(n) = (2*9^n + 3^n)/3. %p A082413 seq((2*9^n+3^n)/3,n=0..19); # _Nathaniel Johnston_, Jun 26 2011 %Y A082413 Cf. A082412, A082414. %K A082413 easy,nonn %O A082413 0,2 %A A082413 _Paul Barry_, Apr 23 2003