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 A198480 #25 Sep 08 2022 08:45:59
%S A198480 1,13,97,685,4801,33613,235297,1647085,11529601,80707213,564950497,
%T A198480 3954653485,27682574401,193778020813,1356446145697,9495123019885,
%U A198480 66465861139201,465261027974413,3256827195820897,22797790370746285
%N A198480 a(n) = 2*7^n - 1.
%H A198480 Vincenzo Librandi, <a href="/A198480/b198480.txt">Table of n, a(n) for n = 0..1000</a>
%H A198480 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (8,-7).
%F A198480 a(n) = 7*a(n-1)+6, n>0.
%F A198480 G.f.: (1+5*x)/((1-x)*(1-7*x)). - _Vincenzo Librandi_, Jul 06 2012
%F A198480 a(n) = 8*a(n-1) -7*a(n-2). - _Vincenzo Librandi_, Jul 06 2012
%t A198480 CoefficientList[Series[(1+5*x)/((1-x)*(1-7*x)),{x,0,40}],x] (* _Vincenzo Librandi_, Jul 06 2012 *)
%t A198480 2*7^Range[0,20]-1 (* or *) LinearRecurrence[{8,-7},{1,13},20] (* _Harvey P. Dale_, Aug 19 2022 *)
%o A198480 (Magma) [2*7^n-1: n in [0..20]]
%o A198480 (PARI) a(n)=2*7^n-1 \\ _Charles R Greathouse IV_, Dec 28 2011
%o A198480 (Maxima) A198480(n):=2*7^n-1$ makelist(A198480(n),n,0,20); /* _Martin Ettl_, Nov 09 2012 */
%Y A198480 Cf. A081655, A048473.
%K A198480 nonn,easy
%O A198480 0,2
%A A198480 _Vincenzo Librandi_, Oct 27 2011