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 A155605 #16 Jun 12 2015 15:26:54
%S A155605 1,9,57,369,2481,17049,118377,825729,5771361,40373289,282534297,
%T A155605 1977503889,13841818641,96890604729,678227855817,4747575858849,
%U A155605 33232973616321,232630643127369,1628413985330937,11398896347634609
%N A155605 7^n+3^n-1.
%H A155605 Harvey P. Dale, <a href="/A155605/b155605.txt">Table of n, a(n) for n = 0..1000</a>
%H A155605 <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (11,-31,21).
%F A155605 G.f.: 1/(1-7*x)+1/(1-3*x)-1/(1-x). E.g.f.: e^(7*x)+e^(3*x)-e^x.
%F A155605 a(n)=10*a(n-1)-21*a(n-2)-12 with a(0)=1, a(1)=9 - _Vincenzo Librandi_, Jul 21 2010
%F A155605 a(0)=1, a(1)=9, a(2)=57, a(n)=11*a(n-1)-31*a(n-2)+21*a(n-3). - _Harvey P. Dale_, Nov 09 2012
%t A155605 Table[7^n+3^n-1,{n,0,20}] (* or *) LinearRecurrence[{11,-31,21},{1,9,57},20] (* _Harvey P. Dale_, Nov 09 2012 *)
%o A155605 (PARI) a(n)=7^n+3^n-1 \\ _Charles R Greathouse IV_, Jun 11 2015
%Y A155605 Cf. A155588, A155590, A155592, A155593, A155594, A155596, A155597, A155598, A155599, A155600, A155601, A155602, A155603, A155604.
%K A155605 nonn,easy
%O A155605 0,2
%A A155605 _Mohammad K. Azarian_, Jan 25 2009